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ELEMENTARY  CHEMISTRY 

A   LAB  OR  A  TOR  Y  MA  NUA  L 


ELEMENTARY 
CHEMISTRY 

A  LABORATORY  MANUAL 


By 
C.    E.    LINEBARGER 

Instructor  in  Chemistry  in  the 
Lake  View  High  School,  Chicago, 
and  Editor  of  "  School  Science" 


RAND,   McNALLY  &  COMPANY 

CHICAGO  NEW  YORK  LONDON 


vi  Elementary  Chemistry 

the  general  work,  the  last  few  months  of  the  course 
being  given  to  the  simpler  parts  of  it. 

This  Manual  represents  an  attempt  to  fulfill  the 
above  requirements.  It  contains  more  experiments 
than  can  be  performed  in  the  usual  course  so  as  to 
offer  a  considerable  range  and  option.  The  Qualitative 
Analysis  is  confined  to  the  Appendix,  and  may  well 
serve  as  the  basis  for  an  advanced  course. 

The  author  takes  pleasure  in  thanking  the  following 
teachers  for  valuable  criticisms  on  the  manuscript : 
Mr.  Harry  D.  Abells,  Morgan  Park  Academy,  Morgan 
Park,  III.;  Dr.  C.  E.  Boynton,  Robert  Waller  High  School, 
Chicago ;  Miss  Louella  Chapin,  South  Division  High 
School,  Chicago;  Mr.  Harry  Clifford  Doane,  Central 
High  School,  Grand  Rapids,  Midi.;  Mr.  Oscar  R.  Flynn, 
Hyde  Park  High  School,  Chicago;  Mr.  Albert  C.  Hale, 
Boys'  High  School,  Brooklyn,  N.  Y.;  Prof.  Alexander 
Smith,  the  University  of  Chicago;  Mr.  Charles  M. 
Turton,  South  Chicago  High  Scliool,  Chicago;  Prof. 
Theodore  Whittelsey,  Northwestern  University ;  Mr. 
C.  M.  Wirick,  R.  T.  Crane  Manual  Training  High 
School,  Chicago ;  Mr.  E.  C.  Woodruff,  Lake  View  High 
School,  Chicago;  and  Mr.  F.  J.  Watson,  William 
McKinley  High  Scliool,  Chicago. 

He  also  wishes  to  acknowledge  his  indebtedness  to 
the  following  teachers  who  have  read  the  proofs  of  the 
book  and  offered  many  helpful  suggestions  :  Prof. 
Alexander  Smith,  the  University  of  Chicago;  Prof. 
G.  C.  Caklwell,  Cornell  University,  Ithaca,  N.  Y.;  Mr. 
Charles  M.  Turton,  South  Chicago  High  School,  Chicago; 
Mr.  E.  C.  Woodruff,  Lake  Vievv  High  School,  Chicago. 

His  thanks  are  also  due  Mr.  W.  E.  Davis  and  Mr. 
E.  C.  Woodruff  for  the  preparation  of  the  illustrations. 

C.    E.    LlNEBARGER. 

Chicago,  April,  1904.. 


THE  TABLE   OF  CONTENTS 

(Numbers  of  Experiments  follow  the  Titles) 

PAGE 

Introductory i 

Some  Physical  Properties  of  a  Few  Familiar  Sub- 
stances, i  —  Chemical  Properties  of  a  Few  Familiar  Sub- 
stances, 2  —  Physical  and  Chemical  Changes,  3  —  Dry  and 
Wet  Reactions,  4 — Reactions  in  Gases,  5  —  Reaction  Due 
to  Light,  6  —  Mixtures  and  Compounds,  7 —  Law  of  Con- 
servation of  Matter  (Persistence  of  Mass),  8. 

Oxygen ...     14 

Oxygen  from  Silver  Oxid,  9 — Oxygen  from  Mercuric 
Oxid,  10 — Oxygen  from  Potassium  Chlorate,  from  a  Mix- 
ture of  Potassium  Chlorate  and  Manganese  Dioxid,  n  — 
Preparation  of  Oxygen  from  a  Mixture  of  Potassium  Chlo- 
rate and  Manganese  Dioxid,  12  —  Oxygen  from  Sodium 
Peroxid  by  Action  of  Water,  13 — Properties  of  Oxygen,  14. 

Ozone 21 

Preparation  of  Ozone,  15 —  To  Find  the  Weight  of  One 
Liter  of  Oxygen,  16  —  To  Find  the  Percentage  of  Oxygen 
in  Potassium  Chlorate,  17. 

Hydrogen 26 

Hydrogen  from  Acids  by  Action  of  Zinc,  18  —  Proper- 
ties of  Hydrogen,  19  —  Transpiration  of  Hydrogen,  20  — 
Combustion  of  Hydrogen,  21  —  Oxidation  and  Reduction, 
22 — Hydrogen  from  Water  by  Action  of  Sodium,  23  — 
Hydrogen  from  Steam  by  Action  of  Magnesium,  24  — 
Hydrogen  from  Steam  by  Action  of  Iron,  25  —  Hydrogen 
from  Solutions  of  Caustic  Alkalis  by  Action  of  Aluminum, 
26  —  Hydrogen  from  Sodium  Hydroxid  by  Heating  with 
Iron  Powder,  27  —  Hydrogen  from  Calcium  Hydroxid  by 
Action  of  Iron  Powder  or  Zinc  Dust,  28. 

Water 34 

Dissolved  Matter  in  Different  Waters,  29  —  Distillation, 
30  —  Coagulation  Filters,  31  —  Conditions  Effecting  Solu- 
tions,   32  —  To    Determine    the    Solubility    of    Potassium 
[vii] 


viii  Elementary  Chemistry 

PAGE 

Dichromate  in  Water,  33  —  To  determine  the  Solubility  of 
Air  in  Water,  34 — Heat  Effects  of  Solution,  35  —  Super- 
saturation,  36  —  Water  of  Crystallization,  37  —  To  Find  the 
Percentage  of  Water  of  Crystallization  in  Gypsum,  38  — 
Deliquescence,  39 — Efflorescence,  40  — Test  for  Water,  41 

-  To'Ascertain  the  Volumetric  Composition  of  Water,  42. 

Hydrogen  Dioxid 43 

Hydrogen  Dioxid  by  Action  of  Sodium  Peroxid  on 
Water,  43  —  Hydrogen  Dioxid  by  Action  of  Sulfuric  Acid 
on  Barium  Dioxid,  44 — Properties  of  Hydrogen  Dioxid,  45 

-  To  Verify  the  Law  of  Definite  Proportions  by  Weight, 
46  —  To  Verify  the  Law  of  Definite  Proportions  by  Vol- 
ume, 47  —  To  Verify  the  Law  of  Multiple  Proportions,  48. 

Nitrogen  and  Its  Hydrogen  Compounds 47 

Separation  of  Nitrogen  from  the  Air,  49  —  Nitrogen  by 
the  Decomposition  of  Ammonium  Nitrate,  50 — Nitrogen 
from  Potassium  Nitrate  by  Action  of  Iron  Powder,  51  — 
Ammonia  from  Ammonium  Salts  by  Action  of  Caustic 
Alkalis  or  Lime,  52  —  Ammonia  from  the  Destructive 
Distillation  of  Some  Animal  Substances,  53  —  Preparation 
and  Properties  of  Ammonia,  54  —  Ammonia  by  the  Inter- 
action of  Potassium  Nitrate,  Potassium  Hydroxid,  and 
Iron  Powder,  55. 

Carbon 51 

Formation  of  Charcoal,  56  — Graphite  from  Pig  Iron,  57 
—  Preparation  of  Lampblack,  58  —  Density  and  Porosity 
of  Charcoal,  59  —  Adsorption  of  Gases  by  Charcoal,  60  — 
Reduction  by  Charcoal,  61  — Decolorizing  Action  of  Bone- 
black,  62 — Combustibility  of  Different  Forms  of  Carbon,  63. 

The  Compounds  of  Carbon  with  Oxygen 54 

Carbon  Dioxid  a  Product  of  Combustion,  64  —  Carbon 
Dioxid  Given  Off  in  Respiration,  65  —  Carbon  Dioxid  Pro- 
duced by  Fermentation,  66  — Carbon  Dioxid  from  a  Car- 
bonate by  Action  of  an  Acid,  67 — Properties  of  Carbon 
Dioxid,  68 — Action  of  Carbon  Dioxid  on  Litmus,  69  — 
Carbon  Dioxid  Absorbed  by  Sodium  or  Potassium  Hydroxid 
Solutions,  70  —  Carbon  Dioxid  in  Solution  Dissolves  Cal- 
cium Carbonate,  71  —  Carbon  Monoxid  by  Action  of  Sul- 
furic Acid  on  Sodium  Formate,  72  —  Carbon  Monoxid  by 


The  Table  of  Contents  ix 

PAGE 

the  Action  of  Sulfuric  Acid  on  Potassium  Ferrocyanid,  73 

—  Oxids  of  Carbon  from  Oxalic  Acid,  74  —  To  Find  the 
Weight  of  a  Liter  of  Carbon  Dioxid,  75. 

Nitrogen  and  Hydrogen  Compounds  of  Carbon       ....     60 

Methane  from  Sodium  Acetate  by  Action  of  Soda-lime., 
76  —  Ethylene  from  Alcohol  by  Action  of  Sulfuric  Acid,  77 

—  Acetylene  by  Action  of  Water  on  Calcium  Carbid,  78  — 
Destructive  Distillation,  79  —  A  Simple  Gas  Factory,  80  — 
A  Candle  as  a  Gas  Factory,  81. 

The  Atmosphere 62 

To  Determine  the  Percentage  of  Oxygen  in  the  Air,  82 

—  Volume  of  Oxygen  in  Air,  83  —  Action  of  Dust  on  the 
Precipitation  of  Water  Vapor,  84 —  To  Find  the  Weight  of 
a  Liter  of  Air,  85. 

Fire  and  Flame 66 

Kindling  Temperature,  86  —  Structure  of  Flame,  87  — 
Luminosity  of  Flame,  88  —  Speed  of  Propagation  of  Flame, 
89  —  Oxidizing  and  Reducing  Flames,  90. 

Salts,  Acids,  and  Bases 68 

General  Properties  of  Acids,  91  —  General  Properties  of 
Bases,  92  —  Neutralization,  93. 

Oxids  of  Nitrogen  ;   Nitric  Acid 69 

Preparation  and  Properties  of  Nitrous  Oxid,  94  — Nitric 
Oxid  ;  Its  Preparation  and  Properties,  95  —  Volumetric 
Composition  of  Nitric  Oxid,  96  —  Nitrogen  Dioxid,  97  — 
Illustration  of  the  Law  of  Volumetric  Proportions,  98  — 
Preparation  and  Properties  of  Nitric  Acid,  99 — Decompo- 
sition of  Nitric  Acid  by  Heat,  100 — Reduction  of  Nitric 
Acid  to  Ammonia,  101  —  Reduction  of  a  Nitrate  to  a 
Nitrite,  102. 

Preparation  and  Properties  of  Acids,  Bases,  and  Salts  .     .     75 

Preparation  of  a  Salt  by  Direct  Union  of  the  Elements, 
IO3  —  Preparation  of  a  Salt  by  the  Solution  of  a  Metal  in 
an  Acid,  104 — Preparation  of  a  Salt  by  Neutralization  of 
Ammonium  Hydroxid  by  Hydrochloric  Acid,  105  —  The 
Solubility  Product,  106. 


x  Elementary  Chemistry 

PAGE 

The  Halogens  and  Their  Hydrogen  Compounds 78 

Chlorin  by  Oxidization  of  Hydrochloric  Acid,  107  — 
Preparation  of  Chlorin,  108-109  —  Properties  of  Chlorin,  no 

—  Chlorin    Water,    in  —  Preparation    and    Properties   of 
Bromin,  112  —  Preparation  and  Properties  of  lodin,  113  — 
Tests  for  Free  Bromin  and  lodin,  114  —  Action  of  Concen- 
trated Sulfuric  Acid  on  Halid  Salts,  115  —  Preparation  and 
Properties  of   Hydrochloric  Acid,    116  —  Analysis  of    Hy- 
drogen   Chlorid,   117  — Tests  for  Chlorids,   Bromids,   and 
lodids,  118  —  To  find  the  Atomic  Weight  of  Chlorin,  119  — 
To  Ascertain  the  Strength  of  a  Given  Sample  of  Hydro- 
chloric Acid,  120  —  To  find  the  Strength  of  a  Given  Sample 
of  Nitric  Acid,  121. 

The  Alkali  Metals 89 

Properties  of  Sodium  and  Potassium,  122  —  Preparation 
and  Properties  of  Potassium  Carbonate,  123  —  Preparation 
and  Properties  of  Sodium  and  Potassium  Hydroxids,  124 

—  Preparation  and  Properties  of  Ammonium  Amalgam, 

125  —  Solvay  Process  of  Sodium  Carbonate  Manufacture, 

126  — Flame   Tests,   127  — Preparation   and   Properties  of 
the  Nitrates_of  the  Alkali  Metals,  128  — Test  for  a  Nitrate, 
129. 

Equivalent  Weights 93 

Equivalent  of  Sodium,  130 — Equivalent  of  Zinc,  131  — 
Equivalent  of  Magnesium,  132 — Equivalent  of  Zinc,  133 — 
To  Determine  the  Vapor  Density  of  Alcohol  by  Dumas' 
Method,  134. 

Sulfur  and  Its  Compounds 97 

Properties  of  Sulfur,  135 — Preparation  and  Properties 
of  Hydrogen  Sulfid,  136  —  Preparation  of  Sulfur  Dioxid, 
137  —  Properties  of  Sulfur  Dioxid,  138  —  Properties  of 
Sulfurous  Acid,  139  —  Properties  of  Sulfuric  Acid,  140. 

Phosphorus 100 

Physical  Properties  of  Phosphorus,  141  —  Conversion 
of  Red  Phosphorus  into  Yellow  Phosphorus,  142  —  Prepa- 
ration and  Properties  of  Phosphin,  143  —  Preparation  of 
Metaphosphoric  Acid,  144 — Preparation  of  Orthophos- 
phoric  Acid,  145  —  Reactions  of  Phosphates,  146. 


The  Table  of  Contents  xi 

PAGE 

Arsenic  and  Antimony 103 

Properties  of  Arsenic,  147  —  Arsin,  148  —  Arsenic  Tri- 
oxid,  Trichlorid,  and  Trisulfid,  149  —  Arsenic  Acid,  150  — 
Properties  of  Antimony,  151  —  Stibin,  152  —  Antimony 
Trioxid,  Trichlorid,  and  Trisulfid,  153. 

Bismuth 105 

Properties  of  Bismuth,  154  —  Reactions  of  Salts  of  Bis- 
muth, 155. 

Magnesium 106 

Properties  of  Magnesium,  156 — Reactions  of  Mag- 
nesium Salts,  157 — Preparation  of  Magnesium  Sulfate, 
158  —  Preparation  and  Properties  of  Calcium  Oxid  and 
Hydroxid,  159  — Properties  of  Calcium  Compounds,  160 

—  Reactions  of  Strontium  and  Barium  Salts,  161. 

Boron  and  Silicon     , 108 

Preparation  of  Boric  Acid,  162  —  Characteristic  Reac- 
tion of  Boron  Compounds,  163  —  Borax  Bead,  164  —  Prep- 
aration of  Magnesium  Silicid  and  of  Silicon  Hydrid,  165 

—  Preparation  of  Silicic  Acids,  166. 

Zinc no 

Properties  of  Zinc,  167  —  Reactions  of  Zinc  Salts,  168 

—  Blowpipe  Reactions,  169. 

Cadmium no 

Properties  and  Reactions,  170. 

Mercury in 

Preparation  of  Mercury,  171  —  Mercurous  Nitrate,  172 

—  Mercuric  Nitrate,  173 — Reactions  of  Mercurous  Salts, 
174 —  Reactions  of  Mercuric  Salts,  175. 

Aluminum 112 

Properties  of  Aluminum,  176  —  Action  of  Acids  and 
Alkalis  on  Aluminum,  177  —  Action  of  Mordants,  178  — 
Alums,  179 —  Reactions  of  Aluminum  Compounds,  180. 

Tin 114 

Physical  Properties,  181  —  Crystallization  of  Tin,  182  — 
Action  of  Acids  on  Tin,  183 — Preparation  of  a  Solution 
of  Stannic  Chlorid,  184 — Distinction  Between  Stannous 
and  Stannic  Salts,  185  —  Replacement  of  Tin  by  Zinc,  186 

—  To  Determine  the  Equivalent  of  Tin,  187. 


xii  Elementary  Chemistry 

PAGE 

Lead 116 

Physical  Properties  of  Lead,  188  —  Deposition  of  Lead 
by  Zinc,  189  —  Action  of  Acids  on  Lead,  190  — Prepara- 
tion and  Properties  of  Lead  Monoxid,  191  —  Preparation 
and  Properties  of  Red  Lead,  192  —  Preparation  and 
Properties  of  Lead  Dioxid,  193  —  Reactions  of  Lead  Salts, 
194  —  Action  of  Water  on  Lead,  195. 

Copper 118 

Properties  of  Copper,  196  —  Precipitate  of  Copper,  197 
—  Preparation  of  Cuprous  Oxid,  198  —  Reactions  of  Cop- 
per Salts,  199  —  To  Find  the  Equivalent  of  Copper,  200. 

Silver 120 

Preparation  and  Properties  of  Silver,  201  —  Reactions 
of  Silver  Salts,  202. 

Iron 121 

Properties  of  Iron,  203  —  Reactions  of  Ferrous  Salts, 
204  —  Reactions  of  Ferric  Salts,  205  —  Oxidation  of  Fer- 
rous Salts,  206 — Reduction  of  Ferric  Salts,  207 — Manu- 
facture of  Ink,  208 —  Borax  Bead  Test  for  Iron,  209. 

Nickel       124 

Reactions  of  Nickel  Salts,  210. 

Cobalt       124 

Reactions  of  Cobalt  Salts,  211  —  Analysis  of  a  Nickel 
Coin,  212. 

Chromium  and  Manganese 125 

Reactions  of  Chromic  Salts,  213  —  Borax  Bead  Test  for 
Chromium,  214  —  Reduction  of  Chromates  to  Chromic 
Compounds,  215 — Properties  of  Chromates,  216 — Reac- 
tions of  Manganous  Salts,  217  —  Borax  Bead  Test  for 
Manganese,  218  —  Oxidation  with  Potassium  Perman- 
ganate, 219. 

Some  Organic  Compounds 127 

Preparation  of  Aldehydes,  220  — Preparation  of  Ethyl 
Acetate,  221  —  Preparation  of  Soap,  222  —  Fehling's  Test 
for  Sugar,  223  —  Preparation  of  Oxalic  Acid,  224 —  Prepa- 
ration of  Nitrobenzene,  225  —  Preparation  of  Aniline,  226. 


The  Table  of  Contents  xiii 

PAGE 

APPENDIX  A 

Qualitative  Analysis i 

Introductory  —  Hydrochloric  Acid  Group  —  Hydrogen 
Sulfid  Group  —  Ammonium  Sulfid  Group  —  Ammonium 
Carbonate  Group  —  The  Alkali  Metals :  Ammonium, 
Sodium,  Potassium. 

APPENDIX  B 
The  Metric  System  of  Weights  and  Measures     ....    xvii 

APPENDIX  C 

Instruments  for  Weighing  and  Measuring xix 

The  Thermometer — The  Barometer —  Balances — Grad- 
uated Vessels. 

APPENDIX  D 

Tables xxvi 

Physical  Constants  of  some  of  the  Elements  —  Tension 
of  Water  Vapor  —  Solutions  to  be  Prepared. 

APPENDIX  E 

Significant  Figures  and  Forms  of  Record  in  Quantitative 

Work       xxxi 

APPENDIX  F 

Laboratory  Equipment xxxvi 

List  A,  Individual  Apparatus  —  List  B,  Table  Appa- 
ratus —  List  C,  Demonstration  Apparatus  —  List  D, 
Chemicals. 


EXPERIMENTS 


INTRODUCTORY 

EXPERIMENT  i.  Some  Physical  Properties  of  a 
Few  Familiar  Substances.  What  information  do 
your  senses  of  sight,  of  smell,  of  taste,  of  hearing,  and 
of  feeling  give  you  in  regard  to  the  following  sub- 
stances :  Charcoal,  sulfur,  paraffin,  common  salt  (sodium 
chlorid),  sugar,  naphthalene  (moth  balls),  borax,  salt- 
peter (potassium  nitrate),  alcohol  ?  Tabulate  the  results 
of  your  observations  in  the  form  outlined  below. 

Put  some  (Smm-  or  icm-  circle1)  of  each  of  the  sub- 
stances examined  above  in  a  test  tube  (a  separate  tube 
for  each  substance),  fill  the  tube  a  third  full  of  water, 
and  note  whether  the  substance  sinks  or  swims.  Shake 
the  substance  and  water  well  together2  and  see  if  it 
dissolves.  Heat  the  water  to  boiling3  in  the  flame  of  a 
Bunsen  burner4  and  note  anything  that  happens.  Set 
the  tubes  aside  until  cold  (leave  the  one  containing 
the  charcoal  for  several  hours)  and  note  any  changes. 
Tabulate  your  observations  in  the  form  outlined  below: 


Behavior  in 

Water 

SUBSTANCE 

Sight 

Smell 

Taste 

Hear- 

Feeling 

Specific  gravity, 
solubility,  etc. 

ing 

Cold 

Hot 

color 

odor 

sweet 

ring 

hard 

opacity 

sonr 

thud 

soft 

etc. 

etc. 

etc. 

[I] 


Elementary  Chemistry 


Fig.    I ONE  WAY  OF  SHAKING  THE  CONTENTS 

OF  A  TEST  TUBE 


Which  of  your  senses  gives  you  the  most  information  ? 
What  tests  serve  to  identify  each  of  the  substances? 

NOTE  i.    Estimation  of  Amounts  of  Substances.    Many  chem- 
icals come  in  powdered  form  or  may  be  easily  reduced  to  a  powder. 

If  a  circle  of  given  diameter  be  drawn  on  a  piece  of  paper  and  as 

much  of  the  powder  as 
possible  placed  upon  it  so 
as  to  form  a  conical  heap 
whose  base  is  the  circle, 
fairly  definite  amounts  of 
the  powder  are  obtained. 
In  the  directions  the 
diameter  in  centimeters 
is  given  right  after  the 
weight  in  case  the  sub- 
stance in  use  is  a  powder; 
as,  (scm-  circle).  If  the 
substance  is  not  powdered 
and  it  is  not  convenient 
to  reduce  it  to  a  powder, 

the  amount  may  be  expressed  in  terms  of  the  size  of  a  single  piece; 

this  is  given  in  millimeters.      Thus,   b»im.  means  that  a  piece 

should  be  selected  or  prepared  that  is  equivalent  in  size  to  one  of 

spherical  shape  &mm.  \\\  diameter. 

Such  estimations  need  not  be  made 

very    accurately,    as   even    rather 

wide  deviations  will  not  essentially 

affect  the  experiment. 

Note  that  the  unit  employed  in 

designating  amounts  of  powders  is 

centimeters,    while    that    used   in 

denoting  the  size  of  single  pieces  is 

millimeters. 

NOTE  2.     To  Shake  a  Liquid 

and    Solid   Together   in  a  Test 

Tube,    (i)  Gently  tap  the  rounded 

end  of  the  tube  held  as  horizontally 

as  possible  in  the  palm  of  the  hand 

(Fig.  i).      (2)  Close  the  tube  with 

the  thumb  and  invert  it.     The  first 

method  is   to  be  used   when   the 

liquid  is  hot  or  corrosive. 

NOTE  3.    Handling  Test  Tubes. 

Test  tubes   may   be  held  by  the 

upper  end  in  the  lingers  (Fig.  2) 

generally  without  inconvenience, 

but  if  the  liquid  is  to  be  boiled  for 

some  time  or  the  substance  is  to  be  heated  to  a  high  temperature 

in  the  test  tube,  it  may  be  grasped  and  held  with  a  test  tube 

holder,  several  forms  of  which  are  on  the  market.      A  serviceable 


Fig.    2 TEST  TUBE-HEED  IN  THE- 

FINGERS 


Experiments 


test  tube  holder  may  readily  be  made  of  rather  stout  wire,  the  ends 
of  which  are  twisted  into  coils  into  which  the  tube  just  fits,  while 
the  middle  part  is  twisted  together  and  inserted  in  a  handle  of 
wood  or  cork  (Fig.  3).  A  substitute  for  a  test 


Fig.   3 TEST  TUBE 

HOLDER 


tube  holder  is  a  strip  of  paper  folded  and  passed 
around  the  test  tube  just  below  its  mouth  so 
that  the  two  ends  of  the  paper  may  be  held 
between  the  thumb  and  forefinger  (Fig.  4)  or 
by  tongs  (Fig.  5). 

In  heating  test  tubes  containing  a  liquid,  the 
outside  of  the  tube  must  be  dry  and  the  glass 
heated  uniformly  and  gradually.  It  should  be 
held  in  the  upper  part  of  the  flame  and  should 
at  first  be  passed  to  and  fro  through  it.  The 
flame  should  never  be  allowed  to  touch  any 
part  of  the  tube  which  is  not  covered  on  the 
inside  with  the 
liquid,  as  the 
bare  glass  may 
become  so  high- 
ly heated  that 
if  the  compara- 
tively cold  liquid  touches  it,  it  may 
break.  When  a  liquid  is  being 
boiled  vigorously  in  a  test  tube,  it 
sometimes  happens  that  portions 
of  the  hot  liquid  are  thrown  out  of 
the  tube  with  considerable  force. 
This  may  be  avoided  by  holding 
the  tube  in  an  inclined  position 
and  continually  rolling  it  to  and 
fro  and  moving  it  around  in  the 
flame.  Be  very  careful  always  to 
hold  the  mouth  of  the  tube  away 
from  yourself  as  well  as  your  neigh- 
bors, so  that  in  case  the  liquid  does 
spurt  out,  it  will  not  harm  any  one. 
Test  tubes  should  always  be 
cleaned  as  soon  as  possible  after 
using.  A  test  tube  swab  or  cleaner  which  compares  favorably 
with  the  bristle  ones  sold  by  the  dealers  may  be  made  out  of  a 
wooden  stick  with  a  bit  of  sponge  or  rag  tied  over  its  end. 

NOTE  4.  Bunsen  Burners.  Bunsen  burners  are  not  only  an 
indispensable  source  of  heat  in  all  laboratories  provided  with  gas, 
but  are  also  used  in  slightly  modified  form  in  gas  stove  and 
"Welsbach"  burners.  The  construction  of  a  Bunsen  burner  is 
shown  in  Fig.  6.  The  gas  enters  at  e  and  passes  up  through 
the  opening  at  in  into  the  tube  n.  Air  is  drawn  in  through  the 
holes  at  the  base  of  n,  and  mixes  with  the  gas.  These  holes  can 
be  more  or  less  closed  by  means  of  a  ring  0,  perforated  with  two 
corresponding  holes  a.  The  mixture  of  gas  and  air  issuing  from 


Fig.  4 TEST   TUBE   HELD    BY 

STRIP  OF  PAPER 


Elementary  Chemistry 


1 


Fitf.    5 TEST  TUBE   HELD   BY  STRIP  OF   PAPER 

GRASPED  BY  TONGS 


the  top  of  the  tube  burns  with  an  almost  non-luminous  flame. 

When  the  supply  of  air  is  cut  off  by  turning  the  ring  b,  the  flame 

becomes      luminous    and 

smoky. 

To  put  a  Bunsen  burner 

in  good  condition, unscrew 

the  tube  «,  and  clean,  if 

necessary,  the  gas  tip  at 

m.    The  ring  should  move 

freely    around    the   tube. 

Put  the  burner  together 

again   and,  connecting  e 

with  the   gas   supply  by 

means  of  rubber  hose  of 

suitable  length,  open  wide 

the  gas  cock.     As  soon  as 

the  gas  seems  to  be  escap- 
ing freely,  light  it.     If  the 

burner  is  in  order  and  the 

airholes    at    in    are    wide 

open,  the  flame  should  be 

blue,  with  the  exception  of  a  minute  yellow  spot  near  the  top  of  the 
flame.     If  this  spot  does  not  appear  in  the 
^  flame,  partially  close  the  airholes  until  it  is 

seen.  If  the  flame  is  at  all  luminous,  even 
when  the  airholes  are  wide  open,  the  supply 
of  gas  is  too  great  for  the  supply  of  air.  So 
unscrew  the  tube  n,  and  make  ;;/  a  little 
smaller  by  pinching  or  hammering  it  together 
somewhat.  If  the  flame  is  too  small  and 
burns  with  a  hissing  noise,  open  ;;/  a  little. 
Never  use  a  burner  unless  it  is  in  perfect  work- 
ing condition.  If  the  gas  supply  is  insufficient, 
the  flame  will  often  "strike  back,"  /.  e.,  the 
gas  will  burn  at  m  instead  of  d.  When  this 
occurs  the  tube  n  soon  becomes  so  hot  that  it 
cannot  be  handled,  and  the  flame  appears 
green  and  smoky,  and  emits  an  unpleasant 
odor.  As  soon  as  you  find  that  a  flame  has 
"  struck  back,"  cut  off  the  supply  of  gas,  and 
after  a  minute  or  so  relight. 

EXPERIMENT  2.  Some 
Chemical  Properties  of  a 
Few  Familiar  Substances. 

Put  a  piece  (3  mm.^  of  charcoal 
in  a  clean  iron  spoon  and 
hold  it  in  a  Bunsen  flame 
(Fig.  7).  Observe  carefully 


Fig.   6 BUNSEN   BURNER 


Experiments 


the  behavior  of  the  charcoal.  Heat  as  hot  as  possible 
until  no  further  change  is  manifest.  Go  through  similar 
operations  with  the  substances  used  in  Experiment  i, 
taking  a  piece  not  larger  than  3  mm-,  and  noting  the 
appearance  of  flame,  color,  and  odor  of  fumes,  appear- 
ance and  relative  amount  of  ash,  and  in  case  the  sub- 
stance does  not  seem  to  burn,  whether  it  swells  up 
or  melts.  Which  of 
the  substances  are  not 
changed  chemically  ? 
What  tests  can  you 
add  to  those  you  found 
in  Experiment  i  ? 

EXPERIMENT  3. 
Physical  and  Chem- 
ical Changes,  (a) 
Hold  a  piece  of  plati- 
num wire  in  a  Bunsen 
flame  for  a  minute  or  so, 
and  note  what  occurs. 
Let  the  wire  cool  and 
see  if  it  has  been  per- 
manently changed. 

(b)  Go  through  the 
same  operations  as  in 
(#),  using  magnesium 

Wire  Or  ribbon  instead        Fig-  T-HEATING  A  SUBSTANCE  IN  A  SPOON 

of  platinum.     Compare  restilt  with  that  obtained  in  (a). 
Compare  the  nature  of  the  changes  in  (a)  and  (b). 

(c)  Wind  tightly  around  one  of  the  ends  of  each 
of  two  electric  light  carbons  (not  "coppered")  about 
10 cm-  of  pieces  of  copper  wire  about  \$cm.  long.     Con- 
nect the  other  ends  of  the  wires  with  a  source  of  elec- 
tricity and  immerse  the  lower  halves  of  the  carbons 
in  a  strong  solution   of   copper  sulfate   (blue  vitriol) 


Elementary  Chemistry 


contained  in  a  beaker  or  tumbler  (Fig-.  8).  Keeping 
the  carbons  about  a  centimeter  apart,  let  the  current 
pass  for  a  few  minutes.  Then  remove  and  examine 
the  carbons.  Is  there  any  evidence  that  a  chemical 
change  has  taken  place  ?  Are  both  carbons  affected  in 
the  same  way  ?  Compare  this  result  with  that  obtained 
by  causing  a  current  of  electricity  to  pass  through  a 
wire  (incandescent  bulb). 

(d)  Place  a  little  (2  cm-  circle)  table  salt  in  a  test 
tube  and  half  fill  the  tube  with  water.  Close  the  tube 
with  the  thumb  and  shake  until  most  of  the  salt  has 
disappeared.  Filter5,  catching  the  filtrate  (the  liquid 
which  passes  through  the  paper)  in  a  clean  evaporating 
dish.  Does  the  filtrate  taste  salty  ?  Set  the  dish  on  a 

ring  of  a  retort  stand 
(Fig.  9)  and  heat,  using 
a  large  flame  and  play- 
ing it  around  so  that 
the  dish  is  heated  uni- 
formly and  the  bottom 
not  more  than  the 
sides.  Conduct  all 


Fig.  8—  ELECTRIC  LIGHT  CARBONS  CONNECTED 
WITH  A  BATTERY  BY  MEANS  OF  COPPER 
WIRES  AND  IMMERSED  IN  A  COPPER  SUL- 


WITH     A     BATTERY     BY     MEANS     OF    COPPER  r  ~  rp,f  ,-,  11  -rr    Qn    fV,  p  f    n  nn  A 

^  S° 


FATE  SOLUTION 


of  t  ft  Q  liquid  may 
spatter  out  of  the  dish  and  be  lost.  As  the  water  boils 
away  a  white  substance  is  deposited,  w^hich,  when  most 
of  the  water  has  been  driven  off,  crackles  or  decrepitates. 
The  decrepitation  is  due  to  particles  of  the  solid  enclos- 
ing minute  amounts  of  water,  which  are  expelled  with 
explosive  violence  when  the  solid  is  heated.  When  the 
decrepitation  ceases  let  the  dish  cool  and  examine  its 
contents.  Give  all  your  reasons  for  thinking  it  to  be 
the  substance  you  take  it  to  be.  Are  the  changes  phys- 
ical or  chemical  ? 


Experiments 


(c)     Put  some  (2  cm-  circle)  powdered  marble  in  a 
test  tube  about  a  third  full  of  water.     Close  the  tube 

with  the  thumb  and 
shake  well.  Does  any 
of  the  marble  seem  to 
dissolve  ?  Decant  the 
liquid,  i.  e.,  pour  it  off 
from  the  solid  so  as  to 
have  as  little  as  pos- 
sible of  the  latter  go 
with  it,  on  a  filter  (Fig. 
10),  and  catch  the  fil- 
trate in  a  clean  evap- 
orating dish.  Heat 
the  dish  as  directed  in 
(d)  until  no  more 
liquid  is  left.  Is  there 
more  than  a  trace  of 
a  solid  residue  ?  What  do  you  conclude  about  the  solu- 
bility of  marble  in  water  ?  Pour6  enough  dilute  hydro- 
chloric acid  on  the  marble  left 
in  the  test  tube  to  fill  it  about 
one-fourth  full.  Warm  gently 
so  as  to  keep  up  a  brisk  evolu- 
tion of  gas.  When  the  effer- 
vescence ceases  filter  through 
a  fresh  filter  paper  and  catch 
the  filtrate  in  a  clean  evapo- 
rating dish.  Now  heat  the 
liquid  and  evaporate  it  to  dry- 
ness.  Is  there  any  decrepi- 
tation ?  Cautiously  taste  a  bit 
of  the  residue  not  larger  than 
a  pin  head.  Does  it  taste 
salty  ?  Point  out  the  physical 


Fig.  9 EVAPORATING  TO  DRYNESS  WITH  FREE 

OR  BARE  FLAME 


Fig.    10 — FILTERING 


Elementary  Chemistry 

2  3 


Fig.   II SUCCESSIVE  STEPS  IN  FOLDING  A  FILTER  PAPER 

and  chemical  changes.  Let  the  dish  containing  the 
residue  stand  for  at  least  twenty-four  hours  and  then 
examine  it.  It  will  probably  have  attracted  moisture 
from  the  air  and  will  be  moist  or  even  liquid  if  the 
amount  of  water  attracted  is  sufficient  to  dissolve  it. 

The  substance  is  on 
this  account  said  to  be 
deliquescent;  its  name 
is  calcium  chlorid. 


Fig.    12 POURING   LIQUID   FROM   A   BOTTLE 

INTO    A   TEST   TUBE 


NOTE  5.  Filtering. 
Filter  paper  is  fitted  into 
a.  funnel  as  follows  :  The 
paper  is  folded  to  form  a 
semi-circle  and  then  a 
quarter  of  a  circle  (Fig.  1 1). 
Three  of  the  quarters  are 

separated  from  the  fourth  so  as  to  form  a  cone  which  is  fitted  into 

the  funnel,  wetted  and  smoothed  around  so  as  to  fit  the  funnel. 
When  pouring  a  liquid  on  a  filter,  direct  the  stream  of  liquid  so 

that  it  strikes  against  the  side  of  the  paper  cone  and  not  into  the 

apex,  otherwise  there  is  danger  of  splashing.     (Fig.  10.) 

The  stern  of  the  funnel  should  touch  the  inside  of  the  receiver 

of    the    filtrate    so    as    to 

prevent  the  formation  of 

drops  which  by  their  fall 

might  occasion  splashing. 
NOTE  6.     Pouring   a 

Liquid  from  a  Bottle.    In 

pouring  hold  the  bottle  in 

the   right  hand  with  the 

thumb  close  to  the  label 

and  the  little  finger  under 

the  bottom  (Fig."i2).     Re- 
move the  stopper  with  the 

second  and  third  fingers 

of  the  left  hand,  the  thumb 

and  first  finger  of  which 


Fig.    13 POURING  FROM  ONE   BOTTLE   INTO 

ANOTHER 


Experiments 


hold  the  test  tube  or  other  receptacle.  Remove  the  drop  of  liquid 
that  may  adhere  to  the  lip  of  the  bottle  by  touching  it  with  the 
stopper,  replace  the  stopper  and  return  the  bottle  to  its  proper 
place.  The  stoppers  and  bottles  may  also  be  held  as  shown  in  Fig. 
13.  Stoppers  should  never  be  placed  upon  the  table  top  except  in 
extreme  cases,  and  then  only  upon  a  piece  of  clean  paper  or  glass. 

EXPERIMENT  4.    Dry  and  Wet  Reactions,    (a]  Rub 

together  in  a  dry  mortar  a  pinch  of  mercuric  chlorid 
with  a  pinch  of  potassium  iodid. 
What  is  the  color  and  solubility 
of  the  product  ? 

(b)  Dissolve  a  pinch  of  mer- 
curic chlorid  in  enough  water  to 
fill  a  test  tube  about  half  full  ; 
also  a  pinch  of  potassium  iodid 
in    about    the   same   volume   of 
water  in  a  second  test  tube.    Mix 
the    solutions.     How    does    the 
color  and  solubility  of  the  prod- 
uct compare  with  that  obtained 
in  (a)  ?    In  which  case  does  the 
reaction    take   place    the    more 
rapidly  ? 

(c)  Mix  together  on  a  piece 
of  dry  paper  about  equal  bulks 
(3  cm-  circle)  of  powdered  sodium 
bicarbonate    (baking    soda)    or 
sodium    carbonate    (washing 
soda)  with  powdered  tartaric  or 
oxalic  acid.     Is  there  any  appa- 
rent change  ?     Put  the  mixture 
in    a    beaker    a   fourth    full    of 
water.     What  happens  ? 

EXPERIMENT  5.  Reactions  in  Gases.  Select  two 
wide-mouthed  bottles  or  jars  of  the  same  size.  Put  in 
one  a  couple  of  drops  of  strong  hydrochloric  acid  and 


Fig.    14 CYLINDRICAL    JARS 

PLACED  MOUTH  TO  MOUTH 


io  Elementary  Chemistry 

cover  the  mouth  of  the  bottle  with  a  card.  Likewise 
put  a  couple  of  drops  of  strong  ammonia  water  in  the 
other.  Move  the  covered  bottles  around  so  that  as 
much  of  their  inside  surfaces  as  possible  may  be  wetted. 
Both  the  liquids  give  off  vapors  which  are  thus  made  to 
fill  the  bottles.  Place  one  bottle  on  the  other  in  an 
inverted  position  (Fig.  14)  and  slip  out  the  cards.  What 
evidence  is  there  that  a  reaction  has  taken  place  ?  What 
is  the  nature  of  the  product  ? 

EXPERIMENT  6.  Reaction  Due  to  Light.  Procure 
a  piece  of  blue-print  paper  which  has  not  been  exposed 
to  a  strong  light  and  tear  it  in  two.  Place  one  of  the 
halves  between  the  leaves  of  a  book  so  as  to  keep  it 
from  the  light  and  expose  the  other  for  ten  minutes  to 
direct  sunlight,  or  if  that  be  not  available,  leave  it  on 
the  desk  until  the  next  laboratory  period.  Place  both 
pieces  of  paper  in  a  dish  and  run  water  over  them  to 
wash  out  any  soluble  coloring  matter  and  compare  the 
color  of  the  two  pieces.  What  evidence  is  there  that  a 
chemical  reaction  has  taken  place  ? 

EXPERIMENT  7.  Mixtures  and  Compounds.  I. 
(a)  Put  a  pinch  of  powdered  iron  or  clean  and  fine 
iron  filings  on  a  piece  of  smooth  paper  and  move  one 
end  of  a  bar  magnet  over  the  underside  of  the  paper 
just  beneath  the  iron.  Can  the  iron  be  drawn  from 
one  part  of  the  paper  to  another  ? 

(b)  Perform  a  similar  experiment  with  powdered 
sulfur  instead  of  iron. 

(c)  Put  a  pinch  of  powdered  iron  in  a  small  test 
tube  and  pour  over  it  enough  carbon  bisulfid  to  fill  the 
tube  about  an  eighth  full.     Shake  thoroughly.     Does 
the  iron  seem  to  dissolve? 

(d)  Decant  the  liquid  into  a  watch  glass  and  allow 
it  to  evaporate  in  the  hood  or  out  of  doors.    Is  more  than 
a  trace  left  ? 


Experiments  I  I 

(c)  Repeat  (c)  and  (d)  with  powdered  sulfur  instead 
of  iron.  What  is  the  residue  ?  How  do  you  know  ? 

(f)  Compare  the  solubility  of  iron  and  sulfur  in 
carbon  bisulfid. 

(g)  Put  a  pinch  of  powdered  iron  in  a  small  test 
tube  and  cover  it  with  dilute  hydrochloric  acid.     What 
occurs  ?    Note  particularly  any  odor.    Wet  a  small  piece 
of  filter  paper  with  a  few  drops  of  lead  acetate  solution 
and  cover  the  mouth  of  the  test  tube  with  it.     Does  it 
change  color  ? 

(//)  Repeat  (g)  with  sulfur  instead  of  iron.  Com- 
pare the  solubility  of  iron  and  sulfur  in  hydrochloric 
acid.  Are  the  above  tests  sufficient  to  distinguish  iron 
from  sulfur? 

(i)  Weigh  out  5.6  ff-  of  powdered  iron  and  3.2  &•  of 
powdered  sulfur  and  mix  them  thoroughly  in  a  mortar. 
What  is  the  color  of  the  mixture  ? 

(j)  Place  a  pinch  of  the  mixture  on  a  piece  of 
paper  and  see  if  you  can  separate  the  iron  from  the 
sulfur  by  moving  a  magnet  under  it  as  in  (a). 

(k)  Put  a  little  of  the  mixture  in  a  small  dry  test 
tube,  add  carbon  bisulfid  and  shake  thoroughly.  Decant 
upon  a  dry  filter  and  catch  the  filtrate  in  a  watch  glass. 
What  is  left  after  the  carbon  bisulfid  evaporates  ?  Com- 
pare with  (d)  and  (c). 

(/)  Place  a  pinch  of  the  mixture  in  a  test  tube  and 
add  dilute  hydrochloric  acid.  Compare  with  (g)  and  (//). 

(;//)  Now  put  all  of  the  mixture  that  remains  in 
a  rather  small  dry  test  tube  and,  using  a  test  tube 
holder,  hold  just  the  rounded  end  of  the  tube  steadily 
in  the  tip  of  a  Bunsen  flame  until  the  lower  part  of  the 
mixture  begins  to  glow.  Then  immediately  remove 
the  tube  from  the  flame. 

(n)  When  the  test  tube  is  cool  lay  it  on  a  piece  of 
paper  and  break  it  by  tapping  it  with  a  pestle.  Separate 


12  Elementary  Chemistry 

the  substance  from  the  particles  of  glass  and  pulverize 
it  in  a  mortar.  Compare  its  appearance  with  that  of  the 
sulfur  and  iron  and  their  mixture  before  heating. 

(o)  Place  a  pinch  of  the  product  on  paper  and  test 
it  with  a  magnet  as  in  (a)  and  (/).  Compare  with  (a). 

(p)  Treat  a  little  with  carbon  bisulfid  as  in  (c),  (d), 
and  (k).  Result? 

(</)  Add  hydrochloric  acid  to  another  portion  as 
in  (£•),  (/?),  and  (/).  Note  the  smell  of  the  gas  and  its 
action  on  lead  acetate  paper.  Compare  with  (g)  and 
(//).  Point  out  all  the  chemical  and  physical  changes 
in  this  experiment.  Are  the  properties  of  the  product 
from  (;//)  different  enough  from  those  of  iron  and  sulfur 
to  characterize  it  as  a  new  substance  ?  Why  were  defi- 
nite amounts  of  the  two  elements  taken  ? 

II.  (a)  Examine  some  gunpowder  for  its  physical 
properties  ;  apply  the  tests  used  in  Experiment  i.  Place 
a  pinch  of  gunpowder  in  a  spoon  and  heat  it  as  you 
did  in  Experiment  2  ;  be  careful  not  to  lean  over  the 
spoon,  as  the  powder  may  flash  up  into  the  face.  Put 
about  3  ff-  (3  cm-  circle)  of  gunpowder  in  a  test  tube  and 
add  enough  carbon  bisulfid  to  fill  the  test  tube  about 
a  quarter  full.  Filter  through  a  small,  dry  filter  paper 
and  catch  the  filtrate  in  a  clean  watch  crystal.  Set  in 
the  hood  to  evaporate  and  determine  by  appropriate 
tests  what  the  residue  is. 

CAUTION.  Carbon  bisulfid  forms  with  air  an 
explosive  mixture.  Do  not  neglect  to  extinguish 
all  flames  within  a  yard  of  you  before  using  it. 

(b]  Spread  out  the  filter  paper  and  shake  out  upon 
it  the  residue  in  the  test  tube,  so  that  the  carbon  bisul- 
fid may  evaporate. 

(r)  Put  this  residue  in  a  test  tube  and  fill  about  one- 
third  full  of  water.  Shake  the  solid  and  the  liquid 


Experiments 


together  thoroughly,  and  heat  for  a  moment  to  boiling. 
Filter  into  an  evaporating  dish,  and  evaporate  to  dry- 
ness  over  a  bare  flame. 

(d)  Examine  the  residue  obtained  as  in  Experiments 
i  and  2.  Give  all  your  reasons  for  thinking  it  to  be  the 
substance  you  take  it  to  be.  Shake  the  black  substance 
remaining  in  the  test  tube  out  on  the  filter  paper  and 
spread  it  out  so 
that  the  water 
may  evaporate. 

(c)  Examine 
•the  residue  when 
dry  to  find  out 
what  it  is,  and 
give  your  proofs 
for  what  you  take 
it  to  be.  Into 
how  many  con- 
stituents have 
you  decomposed 
or  analyzed  gun- 
powder ?  Which 


Fig.  JS  —  CHASLYN  BALANCE  AND  ERLENMEYER  FLASK 
Used  in  illustrating  Law  of  Conservation  of  Matter 


of   them   are    ele- 

ments  ? 

(/)  Put  some  (i  cm-  circle)  saltpeter  in  a  mortar,  add 
about  half  its  btilk  of  sulfur  and  grind  the  substances 
to  a  fine  powder.  Add  an  equal  bulk  of  charcoal  and 
grind  all  well  together,  but  do  not  use  too  great  a  pres- 
sure. Put  a  pinch  of  the  mixture  in  a  spoon  and  apply 
a  flame.  What  happens  ?  What  new  substance  have 
you  prepared  from  saltpeter,  sulfur,  and  charcoal  ?  Is 
it  a  mixture  or  a  compound  ? 

EXPERIMENT  8.  Law  of  Conservation  of  Matter 
(Persistence  of  Mass).  Fit  an  Erlenmeyer  flask  with 
a  tight  stopper  and  fill  the  flask  about  a  third  full  of 


14  Elementary  Chemistry 

strong  lead  acetate  solution.  Fill  a  test  tube  which  is 
small  enough  to  slip  inside  the  flask  with  a  strong  solu- 
tion of  ferric  chlorid  and  carefully  put  it  in  the  flask  so 
as  not  to  mix  the  two  liquids.  Insert  the  cork  tightly 
and  counterpoise  the  whole  on  a  balance.  (Fig.  15.) 
Then  tip  the  flask  upside  down  so  as  to  mix  the  two 
solutions  and,  placing  the  flask  again  upon  the  balance 
pan,  see  if  the  equilibrium  has  been  destroyed.  What 
evidence  is  there  that  a  chemical  action  has  taken 
place  ?  Wherein  does  this  experiment  illustrate  the 
law  in  question  ? 

OXYGEN 

EXPERIMENT  9.     Oxygen  from  Silver  Oxid.     Put 

some  (2  cm-  circle)  silver  oxid  in  a  test  tube  and,  holding 
the  tube  with  tongs  (Fig.  5),  heat  it  in  a  Bunsen  flame. 
Bring  a  splinter  of  wood  with  a  spark  on  its  end  into 
the  mouth  of  the  test  tube  from  time  to  time  and  note 
what  happens.  Heat  until  the  brown  powder  is  turned 
into  a  white  mass.  How  can  you  prove  this  to  be 
silver  ?  How  do  you  know  that  a  gas  is  given  off  ? 

EXPERIMENT  10.  Oxygen  from  Mercuric  Oxid. 
Put  enough  mercuric  oxid  in  an  ignition  tube7  to  fill 
it  to  the  depth  of  about  a  centimeter.  Grasping  the 
tube  with  a  test  tube  holder,  heat  it  in  a  Bunsen  flame, 
very  gradually  raising  its  temperature  as  high  as  pos- 
sible. Note  any  change  in  the  color  of  the  powder  as  it  is 
being  heated.  When  the  tube  is  red  hot,  insert  (with- 
out removing  it  from  the  flame)  a  splinter  of  wood  with 
a  spark  on  its  end.  What  happens?  How  do  you 
account  for  it  ?  After  the  tube  is  cool,  what  is  the  color 
of  the  mercuric  oxid  which  is  left  ?  Is  this  change  of 
color  of  a  physical  or  a  chemical  nature  ?  Examine  the 
deposit  (sublimate}  in  the  upper  part  of  the  tube,  and 
find  out  by  its  physical  properties  what  it  is. 


Experiments  1 5 

NOTE  7.  Ignition  Tubes.  Ignition  tubes  are  made  of  a  spe- 
cial kind  of  glass,  often  called  "hard  glass,"  which  can  with- 
stand a  very  high  temperature  without  melting.  They  should 
be  heated  very  gradually,  as,  being  made  of  thicker  glass  than 
ordinary  test  tubes,  they  are  liable  to  break  the  more  readily 
when  heated. 

To  make  an  ignition  tube,  choose  a  piece  of  hard  glass  (thick- 
walled  ordinary  glass  will  do)  about  8 mm.  in  diameter,  $mm.  in 
bore,  and  12  to  \^cmJ  long.  Heat  the  tubing  in  the  middle  in  a 
Bunsen  flame  (better,  a  blast  lamp  flame)  just  above  the  yellow 
spot,  holding  the  ends  in  either  hand  and  rotating  the  tube  so  as 
to  heat  it  uniformly.  As  soon  as  the  glass  begins  to  soften  and 
yield  a  little,  pull  it  apart  a  little,  keeping  it  in  the  flame  and 
rotating  it  all  the  while.  Draw  it  apart  very  slowly  so  that  the 
glass  of  the  closed  end  may  be  thick  enough.  When  the  tube 
separates  hold  one  part  up  with  its  closed  end  in  the  flame  so  that 
it  may  be  rounded  off  a  little  and,  removing  the  tube  from  the 
flame,  blow  gently  into  it  so  as  to  make  the  end  slightly  bulb- 
shaped.  Let  the  tubes  cool  very  slowly,  /.  e.t  anneal  them  by 
closing  the  airholes  of  the  burner,  and  holding  them  in  the 
smoky  flame  until  they  are  covered  with  a  deposit  of  soot. 

EXPERIMENT  IT.  Oxygen  from  Potassium  Chlo- 
rate, and  from  a  Mixture  of  Potassium  Chlorate 
and  Manganese  Dioxid.  Fill  a  test  tube  to  a  depth 
of  about  2 cm-  with  potassium  chlorate,  and  holding  it 
with  a  test  tube  holder,  heat  the  rounded  end  in  a 
Bunsen  flame.  When  the  solid  melts  and  effervesces 
freely,  insert  a  glowing  splinter  of  wood  into  the  mouth 
of  the  test  tube.  Drop  little  bits  of  wood  (not  more 
than  2  mm.}  down  into  the  effervescing  melt.  What 
happens  ? 

Remove  the  test  tube  from  the  flame  and  as  soon 
as  the  effervescence  ceases,  slide  a  pinch  (be  sure  not  to 
use  too  much)  of  powdered  manganese  dioxid  from  a 
creased  paper  into  the  melted  potassium  chlorate.  In 
what  way  does  the  result  show  that  a  mixture  of  potas- 
sium chlorate  and  manganese  dioxid  gives  off  oxygen 
at  a  lower  temperature  than  the  former  substance 
alone?  WhenUhe  tube  is  cool,  fill  it  with  water  and 
let  it  soak  for  several  hours ;  the  melt  may  then  be 
easily  removed. 


i6 


Elementary  Chemistry 


EXPERIMENT  12.  Preparation  of  Oxygen  from  a 
Mixture  of  Potassium  Chlorate  and  Manganese 
Dioxid.  Mix  about  30^-  (^cm,  circle)  of  powdered 
potassium  chlorate  with  about  a  third  of  its  bulk  of 
manganese  dioxid  and  transfer  to  a  dry  flask  (200  to 
300 c-c-}.  Bore  a  hole  through  a  cork8,  fitting  the  neck 
of  the  flask  so  that  an  L-tube  9> !  °  may  be  pushed 
through  it.  Slip  over  one  branch  of  the  L-tube  one 
end  of  a  piece  of  rubber  tubing  about  30  cm-  long,  whose 
other  end  is  slipped  over  a  delivery  tube  ! ! .  Set  the 
flask  on  a  wire  gauze  ]  2  on  a  ring  of  a  stand  and  secure 
the  neck  of  the  flask  with  a  second  ring  (Fig.  16). 

Alternate  Apparatus.  (Fig.  17.)  A  retort  is  pro- 
vided with  a  delivery  tube  and  is  supported  on  a  ring 
stand  over  a  wire  gauze  or  sand  bath1 2. 

Place  the  mixture  in  the  flask  or  retort,  and  heat 
with  a  small  flame,  removing  the  flame  if  the  evolution  of 

the  gas  becomes 
too  brisk.  Collect 
five  receivers  full 
by  water  displace- 
ment13, and  pass 
to  Experiment  14. 


NOTE  8.    To  Per- 
forate   Corks.      To 

perforate  a  cork,  a 
round  ("rat-tail")  file 
about  i$cm.  long  is 
required.  A  cork  is 
chosen  of  such  a  size 
that  its  narrower  end 
fits  a  little  loosely  in 
the  neck  of  the  flask,  retort,  etc.  The  cork  is  softened  in  a  cork 
squeezer  or  by  rolling  it  on  (i)  the  table  top  under  a  board  ;  or  (2) 
on  the  floor  under  the  sole  of  the  shoe.  The  tip  of  the  tang  of 
the  file  is  heated  to  redness  and  the  red-hot  point  used  to  burn  a 
small  and  regular  hole  through  the  axis  of  the  cork.  This  hole  is 
then  enlarged  with  the  file  until  the  glass  tube  can  just  be  passed 
through  it  by  employing  a  twisting  motion. 


Fig.    l6 HEATING    A    SUBSTANCE    IN     A     FLASK     AND 

COLLECTING  THE  GAS  EVOLVED 


Experiments 


Fig.    17 HEATING  A  SUBSTANCE  IN  A  RETORT  AND  COLLECTING  THE  GAS  EVOLVED 

BY    WATER   DISPLACEMENT 

Cork  borers  may  also  be  used.  These  are  tubes  of  brass  or 
steel,  with  a  cutting  edge,  and  are  of  various  sizes,  so  as  to  cut  a 
hole  of  very  nearly  the  desired  diameter  at  once. 

NOTE  9.  To  Cut  Glass  Tubing.  To  cut  glass  tubing,  a  three- 
cornered  file  about  25  cm.  long  is  needed.  The  tube  is  laid  flat 
upon  the  table,  and  a  deep  scratch  made  with  the  file  at  the  point 
where  the  tube  is  to  be  cut.  The  tube  is  then  grasped  with  the 
two  hands,  one  on  each  side  of  the  scratch,  while  the  thumbs  are 
brought  together  just  at  the  scratch,  but  on  the  side  opposite. 
While  the  fingers  are  pulling  on  the  tube  in  the  direction  of  its 
length,  a  slight  push  with  the  thumbs  across  the  axis  of  the  tube 
usually  suffices  to  break  it  squarely  off. 

When  a  piece  of  glass  tubing  is  cut  the  ends  have  sharp  edges 
which  may  cut  rubber  tubing  slipped  over  them.  The  edges 
should  be  smoothed  down  or  "  fire  polished"  by  gradually  heating 
them  in  a  flame,  all  the  while  twirling  the  tubing  so  that  the 
edges  are  heated  uniformly,  until  the  glass  softens  and  the  sharp 
edges  become  rounded  off,  but  care  should  be  taken  that  the  bore 
of  the  tube  is  not  at  all  lessened. 

NOTE  10.  To  Bend  Tubing.  To  bend  glass  tubing,  hold  it  in 
a  flat  luminous  flame,  such  as  that  offered  by  an  ordinary  gas  jet 
(a  so-called  "bat-wing,"  "fish-tail,"  or  "wing-top"  may  be  put 
on  the  Bunsen  burner).  Rotate  the  tube  and  move  it  to  and  fro 
so  as  to  heat  a  portion  of  the  tube  at  least  ^cm.  in  length.  When 
the  tube  begins  to  soften  let  it  almost  by  its  own  weight  bend 
around  to  the  desired  shape.  Do  not  try  to  bend  it  suddenly  or 
apply  any  considerable  force.  The  bend  should  be  very  gradual 
and  the  bore  of  the  tube  remain  unchanged  in  the  bend.  Always 


i8 


Elementary  Chemistry 


"  fire-polish  "  the  ends  of  the  tube.     Such  a  tube  is  often  called  an 
"L-tube,"  from  its  resemblance  to  the  letter  L. 

NOTE  ii.  Putting  Apparatus  Together.  In  putting  together 
the  parts  of  an  apparatus,  it  is  very  necessary  that  they  make 
tight  joints.  The  corks  should  be  well  softened  and  the  tubes 
inserted  firmly.  It  is  a  good  plan  to  lubricate  glass  tubing  with 
glycerin,  vaseline,  or  even  water.  The  best  way  to  test  an 
apparatus  for  gas-tightness  is  either  to  compress  the  air  in  it  by 
blowing  or  draw  some  out  by  suction.  As  usually  some  part  of 

the  apparatus  is 
under  water,  the 
water  will  thereby  be 
made  to  rise  or  fall  in 
a  tube,  and  if  there  is 
any  leak,  this  water 
will  change  its  level 
when  the  opening 
where  the  lips  were 
applied  is  closed.  To 
attempt  to  use  leaky 
apparatus  is  to  lose 
time  and  labor,  and 
to  insure  the  failure 
of  the  experiment. 

NOTE  12.  Heat- 
ing Glass  Vessels. 
In  heating  glass  ves- 
sels, wire  gauze  (best 
of  copper)  is  usually 
employed.  Sand 
baths  may  also  be 
used,  and  consist  of 
a  shallow  iron  dish  containing  a  little  sand.  Serviceable  ones 
may  be  made  out  of  tin-pail  or  tin-can  covers.  Squares  of  asbestos 
paper  are  also  used  in  many  laboratories.  The  object  of  thus 
interposing  a  screen  is  to  distribute  the  heat  and  render  the  glass 
less  liable  to  crack. 

NOTE  13.  Collecting  Gases  by  Water  Displacement.  This 
method  consists  in  filling  wide-mouthed  vessels  brimming  full  of 
water,  covering  them  tightly  with  a  piece  of  paper,  cardboard 
or  glass,  inverting  them  with  the  cover  pressed  against  the  mouth, 
placing  them  mouth  downward  in  a  dish  filled  with  water  (techni- 
cally named  a  pneumatic  trough),  and  removing  the  cover.  The 
pressure  of  the  atmosphere  keeps  the  water  in  the  vessels,  or 
receivers,  as  they  are  commonly  called.  Most  pneumatic  troughs 
are  provided  with  a  shelf  less  than  an  inch  below  the  surface 
of  the  water  (Fig.  17),  on  which  the  receivers  are  set.  The  gas 
which  is  evolved  is  made  to  pass  up  into  the  receiver  by  means  of 
a  delivery  tube,  and  to  displace  the  water. 

Only  gases  which  are  but  slightly  soluble  in  water  can  be  col- 
lected by  water  displacement. 


Fig.    1 8 STOPCOCK    FUNNEL    GAS    GENERATOR    AND 

CYLINDER  FOR  COLLECTING  THE    GAS 


Experiments 


Fig.  19 — HOME-MADE 

STOPCOCK    FUNNEL, 

NO.  I 


EXPERIMENT  13.  Oxygen  from  Sodium  Peroxid 
by  Action  of  Water.  Fit  a  dry  flask  (200  to  300^-) 
with  a  delivery  tube  and  stopcock  fun- 
nel14. Place  about  20^-  (  7  cm-  circle)  of 
sodium  peroxid  in  the  flask  and  allow 
water  to  drop  slowly  upon  it  from  the 
funnel.  Collect  five  receivers  full  by 
water  displacement13  and  pass  to  Ex- 
periment 14. 

NOTE  14.  Gas  Generators.  Gas  gener- 
ators are  employed  when  a  gas  may  be  formed  by  the  interaction 
of  a  solid  and  a  liquid.  Of  these  there  are  many  styles,  of  which 
those  provided  with  a  stopcock  funnel  are  the  best,  but  stopcock 
funnels  are  expensive.  A  serviceable  stopcock  funnel  may  be 
made  by  the  student  as  follows :  Choose  a  piece  of  rubber  tubing 
that  will  just  slip  into  the  stem  of  a  funnel  and  cut  off  a  piece 
about  -2cm.  long  (Fig.  19).  Cut  a  hole  about  imm-  in  diameter 
near  one  end  and,  warming  the  rubber  a  little,  rub  cement  (made 
by  melting  in  a  dish  two  parts  of  beeswax  with  one  of  rosin) 
around  trie  lower  half  so  as  to  form  a  thin  coating.  Very 
cautiously  (remember  that  funnels  are  made  of  thick  glass  and  are 
very  liable  to  break  if  heated  rapidly  or  unevenly)  warm  the  stem 
of  the  funnel  where  it  commences  to  flare  out  and  push  the  rubber 
tube  into  it.  When  the  glass  is  cold  the  cement 
will  hold  the  rubber  in  position  very  firmly.  Put 
a  little  vaseline  on  a  glass  rod15  that  slips  easily 
but  snugly  into  the  rubber  tubs.  To  close  the 
stopcock,  push  the  rod  down  so  that  it  may  cover 
the  lateral  hole.  To  open  it,  raise  the  rod  more  or 
less  so  as  to  uncover  more  or  less  the  hole.  Such 
a  stopcock  cannot  of  course  be  used  with  liquids 
which  have  any  action  on  rubber.  Pick  out  a 
good  cork  fitting  the  neck  of  the  flask  (or  use  a 
rubber  stopper),  soften  it,  and  perforate  it  with 
two  holes,  through  one  of  which  the  stem  of  the 
funnel  passes,  and  through  the  other  one  of  the 
L-tubes,  forming  a  delivery  tube  (Fig.  18). 

Another  form  of  home-made  stopcock  funnel 
is  the  following  :  A  funnel  tube  is  cut  off  short 
and  connected  with  a  long  piece  of  glass  tubing 
by  means  of  a  bit  of  rubber  tubing  which  can  be  closed  with  a 
pinchcock  (Fig.  20). 

Still  another  form  consists  of  an  ordinary  thistle  or  funnel  tube, 
into  the  stem  of  which  fits  a  bit  of  rubber  tubing  slipped  over  a 
glass  rod.  By  pushing  the  rubber  tube  into  the  stem  of  the  funnel 
and  holding  it  there  by  the  glass  rod,  the  stopcock  is  closed. 


Fig.     20 HOME- 
MADE    STOPCOCK 
FUNNEL,   NO.    2 


20 


Elementary  Chemistry 


EXPERIMENT  14.  Properties  of  Oxygen.  The  first 
receiver  of  gas  caught  in  the  three  preceding  experi- 
ments contains  the  air  that  was  in  the  generator  and  is 
to  be  rejected. 

Attach  a  piece  of  charcoal  to  a  wire,  heat  it  in  a 
flame  until  it  begins  to  glow,  and  then  removing  the 
glass  plate  from  one  of  the  receivers,  insert  it  into  the 
gas  (Fig.  21),  replacing  the  glass  plate  as  far  as  possible. 
The  wire  may  be  thrust  through  a  card  so  that  the 
charcoal  can  be  supported  in  the  center  of  the  receiver. 
Place  a  little  sulfur  in  a  combustion  spoon16,  set  it 
on  fire  by  directing  a  flame  down  upon  it,  and  lower  it 
into  the  second  receiver. 

Put  a  little  red  phosphorus 
in  a  combustion  spoon,  light  it 
thoroughly  and  thrust  it  into  the 
last  receiver.  Keep  the  receiver 
covered  so  that  the  fumes  cannot 
escape  into  the  room. 

Attach  a  piece  of  picture  cord 
wire  to  a  stiff  wire,  fray  out  its 
end  a  little,  heat  it  and  dip  it  into 
sulfur  so  that  some  may  cling  to 
the  wire.  Set  this  on  fire  and  at 
once  introduce  into  a  jar  full  of 
oxygen.  To  prevent  the  intensely 
hot  oxid  of  iron  which  is  formed 
from  breaking  the  receiver,  it 
should  be  a  quarter  full  of  water, 
or  a  layer  of  wet  sand  may  first 
be  put  into  the  vessel.  The  object  of  tipping  the  frayed 
end  of  the  cord  with  sulfur  is  to  raise  the  temperature 
of  the  iron  to  the  kindling  point  so  that  it  too  will  burn. 
What  do  these  experiments  teach  about  combustion  in 
air  and  in  oxygen  ? 


Fig.     21  BURNING     A     SUB- 
STANCE   IN    OXYGEN 


Experiments 


21 


a  b  c  d 

Fig.  22 — COMBUSTION   SPOONS 


NOTE  15.  Stirring  Rods.  To  make  a  glass  stirring  rod,  cut 
off  a  piece  of  solid  glass  rod  of  the  desired  length  and  round  its 
ends  by  holding  it  in  the  flame  of  a  Bunsen  burner.  Stirring  rods 
may  also  be  made  out  of  tubing  by 
heating  its  ends  until  the  glass  runs 
together  and  closes  them  up. 

NOTE  16.  Combustion  Spoons. 
Combustion  or  deflagrating  spoons  are 
little  cups  to  hold  combustible  materials 
to  be  burned  in  a  receiver  of  gas. 
Besides  those  procurable  at  the  dealer 
in  chemical  apparatus  (Fig.  22  a),  ser- 
viceable ones  may  be  improvised  by  (i) 
fastening  an  iron  or  aluminum  thimble 
about  half  full  of  plaster  of  Paris  (which 
has  been  mixed  with  water  and  allowed 
to  set)  to  a  wire  handle  (Fig.  22  6) ;  (2) 
hollowing  out  a  piece  of  chalk  and  fastening  it  to  a  wire  handle 
(Fig.  22  c) ;  and  (3)  twisting  a  wire  around  a  bit  of  asbestos  paper 
(Fig.  22  d\ 

OZONE 

EXPERIMENT    15.     Preparation   of  Ozone.     Put  a 

few  drops  of  ether  in  a  small  flask  and  cork  it  tightly. 
The  ether  will  vaporize  and  a  mixture  of  air  and  ether 
vapor  will  presently  fill  up  the  flask.  Heat  a  stout 
glass  rod  to  redness,  and  plunge  it  into  the  mixture  of 
air  and  ether  vapor.  Smell  of  the  product  cautiously. 
Hold  a  piece  of  iodo-starch  paper  over  the  mouth  of 
the  flask  and  note  any  change  of  color.  Does  ether 
vapor  alone  produce  any  change  of  color  ? 

CAUTION.  Ether  is  very  inflammable.  Do 
not  have  any  flames  near  when  pouring  it  from  a 
bottle. 

EXPERIMENT  16.  (Quantitative^  To  Find  the 
Weight  of  One  Liter  of  Oxygen.  Put  about  5^- 
(i cm-  circle)  of  powdered  manganese  dioxid  in  a  clean, 
dry  evaporating  dish  and  heat  it  as  hot  as  possible  for  at 
least  fifteen  minutes  so  as  to  dry  it  thoroughly.  In  the 
meantime  assemble  an  apparatus  like  that  shown  in 


22 


Elementary  Chemistry 


Fig.  23.  AB  is  a  nine-inch  test  tube  fitted  with  a  two- 
hole  rubber  stopper.  Through  one  hole  passes  a  short 
bit  of  glass  tubing  over  which  a  rubber  hose  provided 
with  a  Hofmann  cock  or  pinchcock  is  slipped  ;  through 
the  other  passes  an  L-tube,  the  shorter  branch  of  which 
fits  into  the  two-hole  stopper  of  an  aspirating  bottle17. 
The  aspirating  bottle,  D,  is  filled  full  of  water,  and  £, 


an    "  acid    bottle, "    about   half   full   of 


Fig.     23 APPARATUS   FOR   FINDING   THE   WEIGHT    OF   A   LITER    OF   OXYGEN 

temperature  of  the  room.  Take  about  20^-  (5  cm- 
circle)  of  dry  potassium  chlorate  and  mix  it  on  a  piece 
of  smooth  paper  with  the  manganese  dioxid,  which 
should  still  be  warm.  Transfer  the  mixture  to  the  test 
tube,  which  has  been  previously  thoroughly  dried,  wipe 
out  any  dust  that  may  cling  to  the  upper  part  of  the 
tube,  and  insert  just  below  the  stopper  a  loose  plug  of 
glass  wool  or  a  coiled  strip  of  previously  ignited  asbestos 
paper,  its  object  being  to  prevent  the  oxygen  from  car- 
rying off  any  solid  particles  in  passing  from  the  tube. 


Experimen  ts  23 

Weigh  the  test  tube  and  contents  to  a  centigram  as 
soon  as  possible  after  rilling. 

Holding  the  tube  horizontally,  tap  it  gently  so  as  to 
make  the  mixture  spread  out  and  lie  along  the  tube, 
and  connect  with  the  aspirating  bottle,  the  tube  being 
supported  on  a  ring  of  a  retort  stand.  Opening  the 
clips  at  F  and  at  H  (use  clip  at  //),  force  water  into  E 
by  blowing  at  F,  so  as  to  drive  all  air  from  the  long 
rubber  tube.  Then  by  suction  draw  water  back  into  D 
until  its  level  reaches  nearly  to  the  stopper,  raise  E  so 
that  the  water  in  D  and  in  E  is  at  the  same  level,  and 
close  F  tightly.  Close  H  and  very  cautiously  remove 
the  rubber  tube  from  E  in  such  a  manner  that  no  water 
escapes  from  the  tube.  Empty  the  water  out  of  E  and 
drain  it  for  a  few  seconds.  Then  place  the  end  of  the 
rubber  tube  in  E  and  open  the  clip  at  H.  A  little  water 
will  flow  out  because  the  level  in  D  is  higher  than  that 
in  £,  but  there  should  not  be  a  continual  flow,  as  that 
would  indicate  that  the  apparatus  was  leaky. 

With  a  small  flame  gently  heat  the  test  tube,  begin- 
ning near  its  mouth.  If  the  mixture  begins  to  froth  at 
the  point  heated,  heat  another  portion  of  it.  The  flame 
must  not  be  held  steadily  at  one  place,  but  played  to 
and  fro  through  a  distance  of  about  3  cm-.  The  glass 
should  not  be  heated  red-hot,  as  there  is  then  danger  of 
a  hole  being  blown  through  it. 

When  the  "acid  bottle"  is  about  three-quarters  full, 
discontinue  the  heating  and  let  the  apparatus  stand 
until  it  cools  to  the  temperature  of  the  room.  In  the 
meanwhile  read  the  barometer.  Then  lift  E  up  or 
down  (it  can  be  lowered  by  bringing  it  down  over  the 
side  of  the  table),  hold  it  so  that  the  level  of  the  water 
remains  the  same  for  a  minute  or  so  in  both  bottles, 
always  keeping  the  end  of  the  rubber  tube  under 
water,  and  close  the  cock  at  H. 


Elementary  Chemistry 


Disconnect  the  test  tube  and  weigh  it  again.  The 
difference  between  this  weight  and  the  one  previously 
found  is  the  weight  of  the  oxygen  evolved. 

Remove  R  without  disturbing  the  water  in  the 
rubber  tube,  and  measure  the  volume  of  water  it  con- 
tains by  pouring  it  out  into  graduated  vessels  (Appen- 
dix BY  or  by  weighing  it  on  a  platform  balance  and 
subsequently  weighing  the  empty  and  drained  bottle. 

Take  the  temperature  of  the  water  and  reduce  the 
volume  of  the  oxygen  to  standard  conditions.  If  this 
reduced  volume  be  denoted  by  v  and  if  the  weight  of 
the  oxygen  be  denoted  by  zv,  the  weight  of  a  liter  may 
be  computed  by  means  of  the  pro- 
portion : 

v  :  iv  ::  1,000  :  x 

The  accepted  value  for  the 
weight  of  a  liter  of  oxygen  is  1.43^-. 
What  possible  sources  of  error  can 
you  point  out  in  the  determination 
of  your  value  ? 

NOTE  17.  Aspirators.  A  large  bottle, 
Z>,  is  fitted  with  a  two-hole  stopper  carry- 
ing two  L-tubes  (Fig.  24).  A  rubber  tube 
a  little  longer  than  the  bottle  is  slipped 
over  the  outlet  tube  and  may  be  closed 
with  a  pinchcock,  //.  To  aspirate  a  gas, 
fill  the  bottle  with  water,  insert  the 
stopper  with  its  tubes,  connect  the  inlet 
tube  with  the  apparatus  furnishing  the 
gas,  B ',  remove  the  pinchcock,  start  the 
water  flowing  so  that  as  it  goes  out  the  gas 
may  be  drawn  into  the  bottle.  Aspirating 
bottles  may  also  be  used  to  store  gases  ;  when  the  bottle  is  full  of 
a  gas,  slip  a  bit  of  rubber  tubing  over  the  inlet  tube  and  close  it 
with  a  pinchcock,  and  then  close  the  outlet  tube.  The  gas  may 
be  forced  out  by  connecting  the  aspirator  with  a  second  one  filled 
with  water  and  placed  at  a  higher  level.  The  water  may  be  made 
to  siphon  over  from  the  second  bottle  into  the  first,  thus  expelling 
the  gas.  The  gas  may  also  be  driven  out  at  B  by  connecting  the 
outlet  tube  with  the  water  supply  of  the  laboratory. 


FlR.  24 ARRANGEMENT  OF 

TUBES    IN    AN    ASPIRATING 
BOTTLE 


Experiments 


EXPERIMENT  17.  (Quantitative^)  To  Find  the  Per- 
centage of  Oxygen  in  Potassium  Chlorate.  Clean 
and  dry  a  porcelain  crucible  and  cover,  place  upon 
a  pipestem  triangle 
(Fig.  25),  and  heat 
gently  at  first  so  as 
not  to  break  the  cru- 
cible, and  then  as  hot 
as  possible  for  two  or 
three  minutes.  When 
the  crucible  is  cool, 
weigh  it  to  a  centi- 
gram (Appendix  B}. 
Put  about  1.5^.  (2«». 
circle)  of  dry  pow- 
dered potassium  chlo- 
rate in  the  crucible 
and  weigh  again. 

Place  the  covered 
crucible  on  the  tri- 
angle and  heat  with  a  Fi8-  25  — HEATING  IN  A  PORCELAIN  CRUCIBLE 

flame  about  5  cm-  high,  which  just  reaches  to  the  bottom 
of  the  crucible.  Lift  the  cover  up  from  time  to  time 
with  the  forceps  and  regulate  the  flame  so  that  the 
melted  potassium  chlorate  is  seen  to  give  off  its  oxygen 
but  slowly.  If  any  should  spatter  up  on  the  cover, 
remove  the  flame,  place  the  cover  bottom  side  upper- 
most on  a  clean  piece  of  smooth  paper,  and  with  a  pin 
loosen  the  layer  of  chlorate  and  return  it  to  the  cruci- 
ble, being  very  careful  that  none  is  lost.  When  the 
bubbling  is  seen  to  slacken,  increase  the  size  of  the 
flame,  and  finally  heat  for  ten  minutes  with  a  flame 
large  enough  to  reach  to  the  top  of  the  crucible  when 
its  yellow  spot  is  just  below  the  bottom  of  the  crucible. 
Let  cool  and  weigh, 


26  Elementary  Chemistry 

Again  heat  very  hot  for  about  five  minutes,  and  cool 
and  weigh  as  before.  If  the  weight  does  not  change, 
pass  to  the  calculations.  If  the  weight  is  less,  heat 
again,  and  continue  in  this  way  until  two  successive 
weights  are  the  same.  This  operation  is  called  heating 
to  constant  weight.  The  loss  of  weight  is  equal  to  that 
of  the  oxygen.  The  percentage  of  oxygen  in  the 
chlorate  is  calculated  thus: 

Weight  of  potass,  chlorate  :  weight  of  oxygen  :  :  100  :  x 

The  accepted  value  for  the  percentage  of  oxygen  in 
potassium  chlorate  is  39.2.  What  is  the  percentage  of 
error  in  your  result  ?  Point  out  any  sources  of  error. 


Fig.    26   —GAS  GENERATOR,  PNEUMATIC  TROUGH,   AND  RECEIVERS 

HYDROGEN 

EXPERIMENT  18.     Hydrogen  from  Acids  by  Action 

of  Zinc.  Arrange  a  gas  generator  as  shown  in  Fig.  26. 
A  wide-mouthed  bottle  is  fitted  with  a  two-hole  stopper 
(best  of  rubber),  through  which  pass  a  funnel  tube18 
and  an  L-tube.  A  piece  of  rubber  tubing  connects  the 
L-tube  with  a  second  one,  thus  forming  a  delivery  tube. 


Experiments 


27 


Cover  the  bottom  of  the  bottle  with  granulated  zinc,  fit 
in  the  stopper,  push  the  funnel  tube  down  so  that  it 
nearly  touches  the  bottom  of  the  bottle,  and  run  in 
through  the  funnel  tube  enough  water  to  just  cover,  and 
thus  seal  its  end.  Pour  dilute  sulfuric  or  concentrated 
hydrochloric  acid19  through  the  funnel  so  as  to  cause  a 
brisk  evolution  of  gas,  and  after  testing  its  purity20, 
collect  four  receivers  full  by  water  displacement  and 
pass  to  Experiment  19. 

As  an  alternate  apparatus  a  stopcock  funnel  gener- 
ator (Fig.  1 8)  may  be  used.  Zinc  is  placed  in  the  bot- 
tle, covered  with  water,  and  strong  hydrochloric  acid 
dropped  in  just  fast  enough  to  make  the  gas  come  off 
briskly. 

NOTE  18.  Funnel  Tubes.  Funnel  tubes  are  tubes  of  glass 
with  one  end  flared  out  to  form  a  funnel,  or  they  may  be  described 
as  small  funnels  with  long  stems.  The  style  shown  in  Fig.  26  is 
sometimes  called  a  "  thistle  tube,"  from  its  fancied  resemblance  to 
the  head  of  a  thistle  A  funnel  tube  should  always  have  its  lower 
end  dip  below  the  liquid  in  a  generator  so  as  to  seal  it. 

NOTE  19.  To  Moderate  Action  of  an  Acid.  If  hydrochloric 
acid  is  used  and  so  much  is  introduced  into  the  generator  that 
hydrogen  is  given  off  too  rapidly, 
a  little  water  poured  through  the 
funnel  will  dilute  the  acid  and  thus 
moderate  its  action. 

CAUTION.    Hydrogen  mixed 
with  air  is  very  explosive. 

NOTE  20.  Testing  Hydrogen. 
Never  perform  experiments  with 
hydrogen  until  you  have  convinced 
yourself  that  the  hydrogen  is  free 
from  air  in  the  following  way  :  Fill 
a  small  test  tube  with  the  gas 
by  water  displacement.  Place  the 
thumb  over  the  mouth  of  the  test 
tube  while  it  is  still  under  water 
and,  bringing  it  close  to  a  flame, 
open  it  so  that  the  gas  may  pass 
into  the  flame  (Fig  27).  If  the  gas 
ignites  with  an  almost  inaudible  report,  it  is  pure ;  if  with  a  loud 
report,  or  sharp  whistle,  it  is  mixed  with  air.  Continue  to  gener- 
ate the  gas  until  it  is  pure  before  collecting  it. 


Fig.    27 DISCHARGING    GAS     FROM 

A  TEST  TUBE  INTO  A  FLAME 


28 


Elementary  CJieviistry 


EXPERIMENT  19.  Properties  of  Hydrogen.  Hold- 
ing a  receiver  full  of  hydrogen  in  an  inverted  position 
(Fig.  28),  thrust  a  lighted  splinter  up  into  the  gas  and 
then  very  slowly  remove  it.  Does  hydrogen  burn  ?  If 
so,  what  is  the  appearance  of  its  flame  ?  Set  a  receiver 
full  of  hydrogen,  with  its  mouth  upward,  on  the  table, 
and  after  waiting  at  least  three  minutes,  insert  a  blaz- 
ing splinter.  How  do  you  account  for  the  result  ?  What 

property  of  hydrogen 
is  hereby  shown?  See 
if  you  can  pour  hydro- 
gen  upward.  How 
can  you  make  sure 
that  hydrogen  is  in 
the  upper  receiver? 
Pressing  a  glass 
plate  or  a  piece  of 
cardboard  tightly 
against  the  mouth  of 
a  receiver  full  of  hy- 
drogen, place  it  in- 
verted upon  a  receiver 
of  the  same  size  filled 
with  air,  and  slip  out 
the  plate  or  card  (Fig. 
14).  After  at  least  five 
minutes  remove  the 

UDDCT    rCCeiVCT     and 

. 

keeping  it  inverted, 
insert  a  lighted  splinter  (Fig  28).  Account  for  the  result. 
What  general  property  of  gases  is  hereby  illustrated  ? 

EXPERIMENT  20.  Transpiration  of  Hydrogen. 
Hold  down  over  the  delivery  tube  (a  straight  tube  is 
substituted  for  the  L-tube)  of  a  gas  generator,  from 
which  hydrogen  is  issuing  rapidly,  a  dry  glass  tube, 


Fig.     28  -  INTRODUCING    A    LIGHTED    SPLINTER 
OF  WOOD   INTO  A   GAS  LIGHTER  THAN  AIR 


Experiments 


29 


closed  at  one  end  with  a  plug  of  plaster  of  Paris,  with  the 

thumb  pressed  over  the  plug-.    In  a  few  minutes  slowly 

lift  the  tube  up,  keeping  it  closed 

with  the  thumb  all  the  while,  until 

it  is  clear  of  the  delivery  tube ; 

then  dip  the  open  end  under  water 

in  a  beaker  or  tumbler  and  remove 

the  thumb  (Fig.  29).    Let  the  tube 

stand  for  at  least  fifteen  minutes, 

examining  it  from  time  to  time. 

Explain  what  occurs. 

EXPERIMENT  21.  Combustion 
of  Hydrogen.  Wrap  several 
folds  of  a  towel  over  and  around 
your  gas  generator  so  that  in  case 
of  an  explosion  the  broken  glass 
can  be  prevented  from  flying 
about.  Test  the  purity  of  the 
hydrogen20,  which  should  be  escaping  quite  rapidly, 
and  then  attach  a  straight  glass  tube  drawn  out  to  a 
jet21  to  the  rubber  tube.  Ignite  the  hydrogen  and 
thrust  the  jet  up  into  an  inverted  beaker.  What  col- 
lects in  the  beaker  ? 

Pinch  the  rubber  tubing  so  as  to  extinguish  the 
flame,  dry  the  inside  of  the  beaker,  and  as  before 
thrust  the  jet  with  unlighted  hydrogen  escaping  from 
it  into  the  inverted  beaker.  What  occurs  ? 

NOTE  21.     Jet  Tubes.    To 

make  a  jet  tube,  select  a  piece 
of  glass  tubing  about  i2««- 
long  and  ^mm.  bore  with  a 
rather  thick  wall.  Heat  the 
middle  in  a  Bunsen  flame, 
twirling  it  so  as  to  heat  it  uni- 
formly. When  it  begins  to 
soften,  slowly  draw  it  out  as  shown  in  Fig.  30.  Cut  it  off  at  the 
narrowest  point,  and  fire-polish  the  wider  ends  of  the  two  jet 
tubes  thus  made. 


Fig.      2Q  APPARATUS     FOR 

SHOWING    TRANSPIRATION     OF 
A  GAS 


Fig.   30 STAGES  IN  MAKING  A  JET  TUBE 


3O  Elementary  Chemistry 

EXPERIMENT  22.  Oxidation  and  Reduction.  Scrape 
a  few  bits  of  copper  foil  or  wire  bright  and  clean  and 
put  them  into  the  middle  of  a  glass  tube  about  30 cm- 
long.  Heat  the  tube  gently  just  below  the  copper,  sup- 
porting it  on  a  ring  stand  with  interposed  wire  gauze, 
and  in  a  slanting  position  so  that  a  draft  of  air  may  pass 
through  it.  Do  not  heat  the  glass  to  redness.  The 
blackening  of  the  copper  is  due  to  the  formation  of 
copper  oxid  ;  the  copper  is  oxidized. 


Fig-   31  PASSING  A  GAS  OVER  A  SUBSTANCE  HEATED  IN   A  TUBE 

Let  the  tube  cool  and  then  slipping  over  one  end  of 
it  a  delivery  tube,  and  connecting  the  other  end  with  a 
hydrogen  generator,  pass  hydrogen  through  it  (Fig.  31). 
After  the  hydrogen  has  been  found  by  test  to  be  pure, 
heat  the  copper.  What  does  the  change  of  color  go  to 
show  ? 

EXPERIMENT  23.  Hydrogen  from  Water  by  Action 
of  Sodium.  With  dry  fingers  and  knife  cut  off  a  piece 
of  sodium  not  more  than  5 mm-  in  diameter22  and  scrape 
it  bright  and  clean.  Wrap  the  bit  of  sodium  up  snugly 
in  a  scrap  of  filter  paper  which  has  been  moistened  in 
kerosene22,  and  using  tongs  bring  it  under  a  large  test 
tube  filled  with  water  and  inverted  in  a  pneumatic 


Experiments 


trough.  Let  go  of  the  sodium  so  that  it  may  rise  into 
the  tube.  If  not  enough  gas  is  generated  to  fill  the  test 
tube,  use  a  second  piece  of  sodium.  Lift  up  the  tube, 
keeping  its  mouth 
down,  and  bring  it  to 
a  flame.  How  do  you 
know  it  contains  hy- 
drogen ? 

NOTE  22.  Sodium 
Must  be  Kept  Dry.  Be 

sure  that  everything  that 
is  used  in  handling  so- 
dium is  dry.  The  object 
of  dipping  the  paper  in 
kerosene  is  to  prevent  a 
too  rapid  access  of  the 
water  to  the  metal.  Too 
much  paper  should  not  be 
used,  else  the  water  will 
be  prevented  from  com- 
ing in  contact  with  the 
sodium. 

EXPERIMENT  24. 
Hydrogen  from 
Steam  by  Action  of 
Magnesium.  Draw 
out  one  end  of  an 
L-tube  so  as  to  form 
a  jet21  and  thrust  the 
other  end  through  a 

Cork     fitting    a    Small       Fig.    32  — HYDROGEN    FROM    STEAM    BY   THE 

flask  (Fig.  32).    Put  a 

little  (only  a  pinch,  for  if  too  much  is  used  the  heat  of 
the  reaction  may  be  so  great  as  to  break  the  tube) 
powdered  magnesium  in  the  tube  and  shake  it  down  so 
that  it  lies  along  the  branch  next  to  the  jet.  Put  a  little 
water  in  the  flask,  insert  the  cork,  and  heat  the  water 
to  boiling  so  that  a  moderate  current  of  steam  passes 


Elementary  Chemistry 


Fig.   33 HYDROGEN  FROM  STEAM  BY  THE  ACTION  OP  IRON 

through  the  jet.  Apply  a  flame  to  the  issuing-  steam 
and  see  if  it  can  be  ignited.  The  little  flashes  of  light 
are  due  to  the  burning  of  tiny  particles  of  magnesium, 
which  are  caught  up  and  carried  along  by  the  steam. 

With  a  second  Bunsen  flame  heat  all  the  horizontal 
branch  of  the  L-tube  hot  enough  to  prevent  the  conden- 
sation of  moisture  in  it.  Then  heat  steadily  the  portion 
of  the  magnesium  farthest  from  the  jet  until  a  reaction 
begins,  and  at  once  remove  the  flame.  Can  the  gas  now 
issuing  from  the  flame  be  set  on  fire  ?  Compare  with 
Experiment  21. 

EXPERIMENT  25.  Hydrogen  from  Steam  by  Action 
of  Iron.  Place  enough  small  brads  in  a  piece  of  gas- 
pipe  (or,  better,  bicycle  tubing)  40  cm-  to  50^-  long  and 
about  2  cm.  bore,  to  fill  the  middle  of  the  pipe  for  a 
distance  of  about  20 cm-f  and  then  fasten  the  pipe  with 
wire  across  a  wide  ring  of  a  stand  (Fig.  33).  Attach  a 


Experiments 


33 


delivery  tube  to  one  end  of  the  pipe  and  to  the  other  an 
L-tube,  with  a  long  pieee  of  rubber  tubing,  making 
connections  with  a  second  L-tube  inserted  in  a  flask 
supported  on  a  second  ring  above  the  pipe.  Bend  a 
thick  piece  of  asbestos  board  into  a  gable-roof  shape 
and  place  it  over  the  pipe.  Put  a  little  water  in  the 
flask  and  arrange  the  ring  supporting  it  so  that  it  nearly 
touches  the  asbestos.  Heat  the  middle  of  the  gaspipe 
as  hot  as  possible,  using  two  burners.  Place  bits  of 
wet  filter  paper  over  the  ends  of  the  pipe  and  keep 
them  dripping  wet  all  the  time  so  as  to  prevent  the 
charring  of  the  corks.  If  the  water  in  the  flask  boils 
too  vigorously,  raise  the  ring  supporting  it  a  little. 
Collect  some  of  the  gas  given  off  and  test  it. 

EXPERIMENT  26.  Hydrogen  from  Solutions  of 
Caustic  Alkalis  by  Action  of  Aluminum.  Place  a 
few  bits  of  aluminum  in  a  test  tube  and  fill  it  about  a 
fourth  full  with  caustic  soda  or  potash  solution.  If  effer- 
vescence is  not  very  brisk,  heat  a  little.  Close  the  tube 
with  the  thumb,  and  after  a  minute  or  so  open  it  so  as  to 
discharge  the  gas 
into  a  flame  (Fig. 
27).  Account  for 
what  occurs. 

EXPERIMENT 
27.  Hydrogen 
from  Sodium 
Hydroxid  by 
Heating  with 
Iron  Powder. 
Make  an  intimate 
mixture  in  a  mor- 
tar of  i  g-  (6  mm-)  of  sodium  hydroxid  and  20^-  (4^-  circle) 
of  iron  powder,  and  introduce  it  into  a  hard  glass  test 
tube  provided  with  a  cork  and  delivery  tube  (Fig.  34). 


Fig.  34 HEATING  A  SUBSTANCE  IN  A  TEST  TUBE 

AND  COLLECTING  THE  GAS  EVOLVED 


34 


Elementary  Chemistry 


Fig.     35  A     COMMON 

FORM    OF   WATER    BATH 


Supporting"  the  tube  on  wire  gauze  and  under  a  ring, 
heat  the  upper  part  of  the  mixture  first  so  as  not  to 
cause  too  brisk  an  evolution  of  the  gas, 
and  collect  it  by  water  displacement. 
EXPERIMENT  28.  Hydrogen  from 
Calcium  Hydroxid  (Lime)  by  Ac- 
tion of  Iron  Powder  or  Zinc  Dust. 
Make  an  intimate  mixture  of  equal 
volumes  (2cm-  circle)  of  dry  calcium 
hydroxid  and  iron  powder,  put  it  into  a  hard  glass  test 
tube  provided  with  a  cork  and  delivery  tube,  and  heat, 
using  a  test  tube  holder,  collecting  the  hydrogen 
evolved  over  water.  Zinc  dust  may  be  used  instead  of 

iron    powder   in    Experi- 
ments 27  and  28. 


WATER 

EXPERIMENT  29.  Dis- 
solved Matter  in  Differ- 
ent Waters.  Slip  a  small 
rubber  band  over  a  test 
tube  about  a  third  of  the 
way  from  its  closed  end, 
fill  it  up  to  the  band  with 
distilled  water,  pour  the 
water  thus  measured  into 
a  clean  evaporating  dish 
(watch  glass  or  saucer), 
and  evaporate  to  dryness 
on  a  water  bath2  3  or  sand 
bath  (asbestos  board)12. 
Note  the  nature  and 


Fig.  36 AN  IMPROVISED  WATER    BATH 


amount  of  any  residue.  Repeat  these  operations  with 
hydrant  water  and  other  natural  waters  which  may  be 
available.  Compare  natures  and  amounts  of  residues. 


Experiments 


35 


NOTE  23.  Water  Baths.  To  avoid  raising  the  temperature 
of  a  substance  above  that  of  boiling  water,  water  baths  are  used. 
A  common  form  (Fig.  35)  consists  of  a  copper  vessel  with  a  cover 
made  of  a  series  of  rings.  By  removing  one  or  more  of  these,  a 
dish  may  be  set  down  nearly  to  its  rim  on  the  bath.  Water  is  kept 
gently  boiling  in  the  bath  so  that  the  dish  may  be  surrounded  by 
steam.  Care  must  be  taken  to  replace  from  time  to  time  the 
water  which  boils  away,  else  the  temperature  will  be  raised  too 
high.  A  serviceable  water  bath  may  be  improvised  with  a  beaker 
(best  with  a  lip)  and  stand  (Fig.  36). 


EXPERIMENT  30.  Distillation.  Fit  one  end  of  a 
long  straight  tube  to  a  retort  or  to  an  L-tube  inserted 
through  the  neck  of  a  flask.  The  other  end  passes  into 

a  test  tube  set  in  a  dish  of 
water.  Fill  the  flask  (Fig. 
37)  or  the  retort  (Fig.  38) 
about  a  third  full  of  water 
and  add  a  piece  of  copper 
sulfate  (3  >«>«.).  Boil  the 
water  in  the  flask  gently 
and  collect  a  test  tube  full 
of  the  distillate.  It  is  well 
to  cover  the  part  of  the  test 
tube  which  is  not  under  water  with  a  piece  of  filter 
paper  which  is  kept  wet  so  as  to  aid  in  the  condensa- 
tion. What  is  the  color  of 
the  distillate  ?  Can  copper 
sulfate  be  totally  separated 
from  water  by  distillation  ? 


Fig-   37  SIMPLE    DISTILLING  APPARA 
TUS,   FLASK  FORM 


Fill  an  evaporating  dish 
about  a  fourth  full  of  alco- 
hol and  set  fire  to  it.  While 
the  alcohol  is  burning,  add  Fig  38_ 
water  in  small  portions  at 
a  time  with  constant  stirring  until  the  flame  goes  out. 
Clean  out  the  retort  or  flask,  and  empty  the  mixture  of 
alcohol  and  water  into  it.  Distill  the  mixture,  collecting 


SIMPLE   DISTILLING  APPARA- 
TUS, RETORT  FORM 


36  Elementary  Chemistry 

enough  of  the  distillate  to  fill  the  test  tube  about  a 
fourth  full.  Pour  the  distillate  into  the  evaporating 
dish  and  try  to  set  it  afire.  What  does  your  result  prove 
about  the  possibility  of  separating  alcohol  and  water  by 
distillation  ?  Which  is  the  more  volatile,  water  or  alco- 
hol ?  Which  has  the  higher  boiling  point  ? 

EXPERIMENT  31.  Coagulation  Filters.  Put  a  pinch 
of  clay  in  a  test  tube  and  fill  with  water.  Shake  the 
water  and  clay  well  together  and  filter  (Fig.  10)  a  por- 
tion of  the  muddy  water  (a  suspension  of  clay  in  water). 
Is  the  filtrate  clear?  Filter  the  filtrate  a  second  time 
and  see  if  it  becomes  clear.  Can  clay  and  water  be 
separated  by  filtration  ?  Now  add  to  the  muddy  water 
a  few  drops  of  alum  solution,  shake  up  thoroughly,  and 
filter  through  a  fresh  filter.  Is  the  filtrate  clear?  If 
not,  add  a  little  more  alum  and  filter  again. 

EXPERIMENT  32.  Conditions  Affecting  Solution. 
(a)  fineness  of  Division.  Choose  two  crystals  of  po- 
tassium dichromate,  alum  or  copper  sulfate,  both  just 
small  enough  to  slip  into  a  test  tube,  and  powder  one 
finely  in  a  mortar.  Put  the  crystal  and  the  powder  in 
separate  test  tubes  and  fill  both  the  tubes  about  half 
full  of  water.  Close  the  tubes  with  the  thumbs  and 
shake  vigorously.  In  which  case  does  solution  take 
place  the  more  rapidly  ?  In  which  case  is  the  surface 
of  contact  between  the  solid  and  the  liquid  the  larger  ? 
To  save  time  in  dissolving  a  solid,  what  preliminary 
operation  ought  it  to  be  subjected  to  ? 

(b)  Temperature.  Put  about  6  £-•  (3  cm-  circle)  of 
powdered  potassium  dichromate  in  a  test  tube,  and  fill 
it  about  a  third  full  of  water.  Shake  the  solid  and 
liquid  well  together  for  some  time.  Does  the  solid  all 
dissolve?  Is  there  a  limit  to  the  solubility  of  a  sub- 
stance at  a  given  temperature  ?  Heat  to  boiling  for  a 
minute  or  so.  Does  the  solid  all  dissolve  now  ?  Cool 


Experiments  37 

the  tube  and  contents  by  letting  cold  water  run  over  it. 
What  happens  ?  What  effect  has  temperature  upon  the 
solubility  of  a  substance  ? 

EXPERIMENT  33.  (Quantitative^)  To  Determine 
the  Solubility  of  Potassium  Dichromate  in  Water. 
Fill  a  flask  (200  to  300 c-c-)  a  fourth  full  of  powdered 
potassium  dichromate,  and  add  sufficient  water  to  fill 
the  flask  about  three-fourths  full.  Cork  the  flask  tightly 
and  place  it  in  a  pneumatic  trough  filled  with  water  at 
the  temperature  of  the  room.  Put  a  thermometer  in  the 
trough  and  read  its  temperature  at  intervals  of  about 
two  minutes,  and  each  time  shake  well  the  solid  and 
liquid  in  the  flask.  The  temperature  should  not  vary  by 
more  than  a  degree  for  at  least  fifteen  minutes.  Filter 
a  portion  of  the  solution  thus  saturated  into  a  weighed 
evaporating  dish  so  as  to  fill  it  about  half  full.  Weigh 
the  evaporating  dish  and  solution  and  then  evaporate 
to  dryness  on  a  water  bath23.  Be  very  careful  not  to 
lose  any  of  the  solid  by  spurting.  Let  the  dish  and  con- 
tents cool  and  again  weigh.  Calculate  the  percentage 
composition  of  the  solution. 

EXPERIMENT  34.  (Quantitative.}  To  Determine  the 
Solubility  of  Air  in  Water.  Shake  a  large  bottle  filled 
about  half  full  of  water  vigorously  for  several  minutes  so 
as  to  saturate  it  thoroughly  with  air.  The  water  should 
be  at  the  temperature  of  the  room,  and  care  should  be 
taken  not  to  warm  it  up  in  shaking  by  the  heat  of  the 
hands.  Fit  a  small  flask  (200  to  300 c-c-}  with  a  stopper 
(best  of  rubber)  and  a  delivery  tube  of  narrow  bore  (not 
more  than  2mm-)  of  the  form  shown  in  Fig.  39.  Set  the 
flask  on  a  ring  of  a  stand  with  interposed  wire  gauze  so 
that  its  delivery  tube  may  come  under  a  test  tube  placed 
in  a  beaker  set  on  a  second  ring  of  the  same  stand.  Fill 
both  the  beaker  and  the  test  tube  with  water,  invert  the 
filled  test  tube  in  the  beaker,  and  pour  out  as  much 


Elementary  Chemistry 


water  as  possible  from  the  beaker  without  the  water  in 
the  test  tube  escaping.  Take  the  temperature  of  the 
water  in  the  bottle  and  fill  the  flask  brimful.  Then 

insert  the  stopper  so 
that  the  delivery  tube 
will  be  filled  with 
water  also.  There 
must  not  be  any  bub- 
bles of  air  either  in  the 
flask  or  the  delivery 
tube. 

Weigh  the  flask, 
delivery  tube,  and  con- 
tents to  decigrams,  set 
the  flask  upon  the  wire 
gauze  so  that  its  deliv- 
ery tube  engages  un- 
der the  test  tube,  and 
heat  with  a  small 
flame,  making  the 
water  boil  vigorously 
until  a  cracking  sound 
is  heard,  indicating 
that  all  the  air  has 
been  expelled  from 
the  water.  Remove  the  delivery  tube  from  the  water 
in  the  beaker  and  stop  heating.  Fill  the  beaker  with 
water  at  the  temperature  of  the  room,  lift  the  test  tube 
up  so  that  the  level  of  the  water  inside  and  outside  is 
the  same,  and  mark  it  with  a  small  level  rubber  band 
slipped  over  the  test  tube.  Remove  the  test  tube  and 
determine  the  volume  of  the  air  driven  out  of  the  water 
either  with  a  burette  (Appendix  B)  or  by  weighing  the 
water  which  fills  the  tube  up  to  the  rubber  band.  Dry 
flask  and  delivery  tube  and  weigh.  Record  results  thus: 


Fig.    39 APPARATUS    FOR    DETERMINING    THE 

SOLUBILITY  OF  AIR  IN  WATER 


Experiments 


39 


Weight  of  water  filling  flask  and  delivery  tube  =  A  <?"• 

Volume  of  air  expelled  at  — °  and  —  mm.  of  mercury  —  B  c.c. 
Volume  of  air  reduced  to  o°  and  760  mm.  of  mercury  =  C  c.c. 
No.  of  c.c.  of  air  at  o°  and  760  mm-  dissolved  by  A  c.c.  of  water. 
No.  of  c.c.  of  air  dissolved  by  1,000  c.c.  of  \vaterat — °  =  DC.C. 
Accepted  value  for  solubility  of  air  in  water  (Appendix  C). 

EXPERIMENT  35.    Heat  Effects  of  Solution.    Have 

ready  at  hand  5.0^-  of  the  solids  named  in  the  table 
below  in  the  form  of  a  fine,  dry  powder.  Measure. 
(Appendix  B)  io.oc-c-  of  water  at  the  temperature  of 
the  room  into  a  test  tube,  insert  a  thermometer,  stir, 
and  read  the  temperature.  Add  all  at  once  the  first  of 
the  powders,  stir  well  with  the  thermometer,  holding 
the  test  tube  with  a  holder  so  as  not  to  warm  the  solu- 
tion with  the  hand,  and  record  the  highest  temperature 
attained.  Repeat  these  operations  with  the  other  sol- 
ids, cleaning  out  the  test  tube  after  each  trial. 

Add  5.0^-  of  alcohol  to  ic-.o^-  of  water  and  find  the 
temperature  of  the  well-stirred  mixture.  Also  add 
5.0^-  of  strong  sulfuric  acid  to  io.oc-c-  of  water  and  take 
the  maximum  temperature.  Record  results  as  follows  : 

HEAT  EFFECTS  OF  SOLUTION 


SUBSTANCES 

Solvent 

Temperature 

Change  of 
Tem- 
perature 

Name 

Amt. 

Name 

Amt. 

Initial 

Highest 

or 
Lowest 

Maxi- 
mum 

Kind 

Ammonium  chlorid.. 
Calcium  chlorid 

Ammonium  nitrate  . 
Potassium  nitrate  
Copper  sulfate  (dehy- 
drated) _  .  

Sugar 

Potassium  carbonate. 
Sodium  carbonate  
Alcohol 

Sulfuric  acid 

40  Elementary  Chemistry 

EXPERIMENT  36.  Supersaturation.  Fill  a  test  tube 
about  a  fourth  full  of  sodium  acetate  (or  sodium  sul- 
fate)  crystals  and  add  barely  enough  water  to  cover 
them.  Heat  cautiously  to  boiling  until  a  clear  solution 
results  and  boil  vigorously  for  a  minute  or  so.  Set  the 
tube  aside  in  a  slanting  position  so  that  any  dust  may 
fall  on  the  sides  of  the  tube  and  not  reach  the  solution. 
After  the  solution  is  cool  drop  into  it  a  very  small  frag- 
ment of  a  sodium  acetate  (sodium  sulfate)  crystal  and 
shake  the  tube.  What  happens  ? 

EXPERIMENT  37.  Water  of  Crystallization.  Place 
in  separate  clean  and  dry  small  test  tubes  a  few  small 
crystals  of  potassium  nitrate,  copper  sulfate,  and  cobalt 
chlorid.  Place  the  test  tubes  on  the  wire  gauze  and 
place  under  them  a  frame  made  of  iron  wire  fashioned 
so  that  while  their  closed  ends  converge  to  a  common 
center,  their  mouths  just  project  beyond  the  gauze  and 
are  lower  than  their  closed  ends.  Adjust  the  flame  of 
a  Bunsen  burner  so  that  it  keeps  red  hot  a  small  circle 
just  below  the  closed  ends  of  the  test  tubes,  being  care- 
ful not  to  let  the  flame  strike  through  the  gauze.  Note 
carefully  the  appearance  of  moisture  in  the  mouths  of 
the  tubes.  In  which  case  is  it  the  most  abundant  ? 
What  changes  do  the  substances  undergo  ?  Which  of 
them  contain  water  of  crystallization  and  which  me- 
chanically enclosed  water  ?  When  the  water  of  crystal- 
lization is  expelled  from  a  substance,  the  substance  is 
said  to  be  dehydrated. 

Using  a  dilute  solution  of  cobalt  chlorid  instead  of 
ink,  write  on  paper  with  a  clean,  new  pen.  Is  the  writ- 
ing almost  invisible  ?  Waft  the  paper  over  a  flame  so 
as  to  \varm  it.  Do  the  characters  now  show  and  in  what 
color?  Breathe  upon  the  writing.  What  happens? 
How  do  you  explain  the  action  of  this  kind  of  sympa- 
thetic ink  ? 


Experiments  41 

EXPERIMENT  38.  (Quantitative.}  To  Find  the 
Percentage  of  Water  of  Crystallization  in  Gypsum. 

Clean  and  weigh  to  centigrams  a  porcelain  crucible 
and  cover.  Place  in  it  enough  gypsum  in  powder  or 
coarse  fragments  to  fill  it  about  a  fourth  full.  Weigh, 
place  it  upon  a  pipestem  triangle  (Fig.  25),  and  heat 
with  a  small  flame  for  about  ten  minutes.  Let  the 
crucible  cool  and  weigh  it.  Heat  the  crucible  once  more 
for  about  five  minutes,  let  cool  and  weigh.  If  it  has 
lost  in  weight,  heat  it  still  again,  and  so  on  to  constant 
weight.  Calculate  the  percentage  of  water  of  crystalli- 
zation contained  in  gypsum. 

Instead  of  a  crucible,  test  tubes  or  clay  pipes  may  be 
used.  A  test  tube  is  weighed,  filled  about  a  sixth  full 
of  gypsum,  again  weighed  and  heated  (held  in  a  test 
tube  holder  in  a  slanting  position)  to  constant  weight. 

EXPERIMENT  39.  Deliquescence.  Put  a  little  solid 
potassium  hydroxid  ($mm-)  in  an  evaporating  dish  or 
watch  glass,  set  it  aside  in  a  safe  place,  and  examine  it 
after  a  few  hours.  Review  Experiment  7.  How  do 
you  account  for  the  change  ? 

EXPERIMENT  40.  Efflorescence.  Choose  a  clear 
crystal  of  sodium  sulfate,  place  it  upon  a  watch  glass  or 
evaporating  dish,  set  it  aside  in  a  safe  place,  and  examine 
it  from  time  to  time.  (It  is  advisable  to  weigh  the  dish 
and  crystal  so  as  to  keep  track  of  any  change  in  weight.) 
What  change  does  the  crystal  undergo  ? 

EXPERIMENT  41.  Test  for  Water.  Expel  the  water 
of  crystallization  from  a  little  copper  sulfate  by  heating 
it  in  an  evaporating  dish  or  a  tin-box  cover.  Place  a 
little  of  the  dehydrated  substance  on  a  watch  glass  and 
add  a  drop  of  strong  alcohol.  Does  the  substance  turn 
blue  ?  Try  carbon  bisulfid,  ether,  kerosene,  or  any  other 
liquids  not  containing  water  which  are  available. 
Finally  try  water.  How  is  the  result  a  test  for  water? 


42  Elementary  Chemistry 

EXPERIMENT  42.  (Quantitative.)  To  Ascertain  the 
Volumetric  Composition  of  Water.  Choose  two  long 
and  narrow  test  tubes  as  nearly  of  the  same  size  as 
possible,  and  slip  over  them  narrow  rubber  bands  or 
tie  around  them  bits  of  cotton  string  to  serve  as 
markers.  Place  one  marker  about  one- third  of  the 
length  of  one  of  the  tubes  from  its  open  end,  and  the 
other  marker  on  the  second  test  tube  about  one-fourth 
of  the  length  of  the  tube  from  the  open  end.  Fill 
both  tubes  with  water  and,  holding  them  in  a  pneumatic 
trough,  let  in  air  until  the  level  of  the  water  inside  and 
outside  is  at  the  markers.  Have  a  hydrogen  generator 
conveniently  at  hand  from  which  hydrogen  is  issuing  at 
the  rate  of  about  two  bubbles  a  second.  Thrust  one  of 
the  test  tubes  over  the  delivery  tube,  and  the  instant 
it  is  filled  with  hydrogen  remove  it  and  set  it  aside  in 
the  pneumatic  trough  with  its  end  under  water.  Do 
likewise  with  the  other  tube.  These  tubes  contain 
definite,  measurable  volumes  of  air  and  hydrogen. 

Now  a  mixture  of  air  and  hydrogen  which  contains 
the  two  gases  in  just  the  right  proportions  totally  to 
combine  and  form  water,  explodes,  when  ignited,  with 
a  sharp,  whistling  sound  ;  otherwise,  if  the  proportions 
are  not  just  right,  the  sound  of  the  explosion  is  fuller 
and  louder.  Close  the  two  tubes  with  the  thumbs 
under  water  and,  bringing  them  on  either  side  of  a 
flame  (Fig.  27),  let  their  contents  pass  into  the  flame  in 
rapid  succession  and  note  the  character  of  the  sounds. 
There  will  probably  be  an  easily  detectable  difference. 

Now  push  the  marker  of  the  test  tube  which  con- 
tained the  greater  volume  of  hydrogen  down  a  little 
(a  couple  of  millimeters),  and  the  other  marker  up 
about  the  same  distance,  thus  making  the  volumes 
more  nearly  equal.  Fill  them  with  air  and  with  hydro- 
gen as  before,  and  ignite  their  contents.  Continue  in 


Experiments  43 

this  way  until  you  can  detect  but  a  slight  difference,  if 
any,  in  the  sound  of  the  explosions,  which  should  be 
more  like  a  whistle  than  a  report. 

Empty  out  the  tubes  and  drain  them.  Ascertain  the 
volume  up  to  the  marker,  either  by  running-  in  water 
from  a  burette  or  by  weighing.  (Appendix  B.)  Fill 
the  tubes  brimming  full  with  measured  amounts  of 
water,  thus  finding  the  volumes  of  the  mixtures  of  air 
and  hydrogen,  whence  by  subtraction  the  volume  of  the 
hydrogen  may  be  ascertained.  As  air  contains  very 
nearly  one-fifth  of  oxygen  by  volume,  one-fifth  of  the 
volume  up  to  the  marker  will  be  the  oxygen  which  has 
combined  with  the  hydrogen.  Enter  results  thus  : 

First  Second 

test  tube.  test  tube. 

Volume  of  air =  A'  c.c.          ~  A  c.c. 

Volume  of  oxygen  (£  of  A) =  B'  c.c.          —  B  c.c. 

Volume  of  hydrogen =  C'  c.c.          —  C  c.c. 

(B-j-B')^-  of  oxygen  combine  with  (C  -f-  C')  c-c- 
of  hydrogen,  whence  i  c-c-  of  oxygen  combines  with 
(C  +  C')/(B  +  B')^-  of  hydrogen.  The  accepted  ratio 
is  i  :  2.  What  are  the  sources  of  error? 

HYDROGEN    DIOXID 

EXPERIMENT  43.  Hydrogen  Dioxid  by  Action  of 
Sodium  Peroxid  on  Water.  Add  a  dozen  or  so  drops 
of  strong  sulfuric  acid  to  about  50^-  of  cold  water  in  a 
beaker  and  stir  well.  Cool  the  solution  as  much  as  pos- 
sible (if  ice  is  available,  put  a  few  pieces  in  the  solution) 
and  add  in  small  portions  with  constant  stirring  about  2#- 
( i  cm.  circle)  of  sodium  peroxid.  Pass  to  Experiment  45. 

EXPERIMENT  44.  Hydrogen  Dioxid  by  Action  of 
Sulfuric  Acid  on  Barium  Dioxid.  Put  about  io#- 
(4  cm.  circle)  of  barium  dioxid  in  a  beaker,  and  moisten 
it  with  a  few  drops  of  water.  Add  about  30  c-c-  of  cold, 


44  Elementary  Chemistry 

dilute  (about  10  per  cent)  sulfuric  acid,  stir  well  for  sev- 
eral minutes,  let  the  solid  settle,  and  decant  the  solution 
of  hydrogen  dioxid  from  the  insoluble  barium  sulfate. 
If  the  filtrate  is  not  clear,  pour  it  upon  the  same  filter 
paper  and  continue  in  this  way  until  it  is  perfectly  clear. 
Pass  to  Experiment  45. 

EXPERIMENT  45.  Properties  of  Hydrogen  Dioxid. 
Action  of  Potassium  Permanganate  Solution.  Fill  a  test 
tube  about  a  fourth  full  of  the  hydrogen  dioxid  solution 
prepared  in  Experiments  43  or  44,  add  a  drop  or  so  of 
potassium  permanganate  solution  and  shake  well.  The 
gas  evolved  is  oxygen.  Continue  adding  the  perman- 
ganate until  the  color  is  not  discharged. 

Action  on  lodo-Starcli  Paper.  Moisten  iodo-starch 
paper  with  a  solution  of  hydrogen  dioxid.  What  effect? 
Where  else  has  this  paper  been  used  ?  W'hat  two  sub- 
stances is  it  a  test  for  ?  How  may  they  be  distinguished 
from  each  other  ? 

Action  on  Potassium  DicJiromate  Solution.  Fill  a 
large  test  tube  nearly  full  of  water  and  add  just  enough 
potassium  dichromate  solution  to  tinge  it  a  very  light 
yellow.  Now  add  a  couple  of  drops  of  sulfuric  acid, 
and  then  a  dozen  or  so  drops  of  hydrogen  peroxid  solu- 
tion. Shake  well  and  note  what  happens.  Pour  some 
out  into  a  dish  and  let  it  stand  for  a  few  minutes.  Fill 
a  small  test  tube  about  a  sixth  full  of  hydrogen  dioxid 
solution  and  add  enough  ether  to  form  a  layer  about 
half  a  centimeter  thick. 

CAUTION.  Do  not  have  any  flames  near  when 
using  ether. 

On  shaking,  do  the  two  liquids  mix  ?  Add  one  drop 
of  potassium  dichromate  solution  and  shake  gently. 
Result  ?  If  you  are  in  doubt  about  the  result  add 
another  drop,  but  do  not  use  too  much  potassium 
dichromate  solution. 


Experimen  ts  45 

EXPERIMENT  46.  (Quantitative.}  To  Verify  the 
Law  of  Definite  Proportions  by  Weight.  Weigh 
out  exactly  2.00  £•  of  sodium  carbonate  (washing  soda) 
in  a  porcelain  evaporating  dish.  Add  concentrated 
hydrochloric  acid,  a  few  drops  at  a  time,  being  careful 
to  avoid  any  loss  from  the  effervescence.  When  the 
sodium  carbonate  is  wholly  dissolved,  evaporate  to  dry- 
ness  (Fig.  9)  and  constant  weight.  The  residue  is  com- 
mon salt. 

Repeat,  using  exactly  4.00  *"•  of  sodium  carbonate. 
Calculate  the  ratio  of  the  sodium  carbonate  to  the  salt 
in  both  cases.  How  do  they  compare  ?  How  is  this  a 
proof  of  the  law  in  question  ? 

EXPERIMENT  47.  ( Quantitative}  To  Verify  the  Law 
of  Definite  Proportions  by  Volume,  (a)  Put  about 
25  c.c.  of  concentrated  hydrochloric  acid  in  a  beaker  and 
mix  with  it  about  an  equal  volume  of  water.  Fill  a 
burette  (Appendix  B)  with  this  mixture.  Also  fill  a 
second  burette  with  concentrated  ammonium  hydroxid. 

(b)  Run  5.0  c-c-  of  the  acid  into  a  weighed  evap- 
orating  dish  and   add    a    couple    of    drops   of   litmus 
solution.     After    reading   the   burette    containing   the 
ammonium   hydroxid,  run   the    ammonium    hydroxid 
into  the  acid  slowly  with  constant  stirring  until  the  red 
color  just  changes  to  blue. 

The  acid  and  ammonium  hydroxid  combine  to  form 
a  solid  —  ammonium  chlorid.  Evaporate  to  constant 
weight  on  a  water  bath. 

(c)  Put  the   same  volume   of  acid  into   a   second 
weighed  evaporating  dish  and  add  twice  as  much  ammo- 
nium hydroxid  as  before.    Evaporate  to  constant  weight 
on  a  water  bath. 

(d)  Run  i o.o  c-c-  of  the  acid  into  a  third  weighed  dish 
and  cautiously  add  just  enough  ammonium  hydroxid  to 
change  the  color.     Evaporate  to  constant  weight. 


46 


Elementary  Chemistry 


(e)  Put  a  few  drops  of  hydrochloric  acid  in  a  dish 
and  evaporate  to  dryness.  Is  there  any  residue  ?  Does 
ammonium  hydroxid  leave  a  residue  when  evaporated  ? 

Try    it    with    a    few 
drops. 

(f)  Compare  the 
weights  of  ammo- 
nium chlorid  obtained 
in  (/;),  (c),  (d).  How 
do  your  results  verify 
the  law  under  discus- 
sion ? 

EXPERIMENT  48. 
(Quantitative.)  To 
Verify  the  Law  of 


Multiple  Propor- 
tions. Arrange  an 
apparatus  as  shown  in 
Fig.  40.  The  cylinder  should  be  of  at  least  500  c-c-  capac- 
ity. Weigh  out  exactly  2.00^-  and  also  4.00 &•  of  baking 
soda  (Appendix  B).  Put  the  larger  amount  in  an  evap- 
orating dish  and  heat  as  hot  as  possible  for  at  least  ten 
minutes.  While  the  heating  is  going  on,  put  the  smaller 
portion  into  the  generator  and  pour  IQC-C.  Of  hydrochloric 
acid  into  the  stopcock  funnel.  Fill  the  cylinder  with 
water  and  invert  it  in  the  pneumatic  trough.  Run  the 
acid  into  the  generator  and  collect  the  carbonic  acid  gas 
given  off.  Be  careful  not  to  let  any  of  the  gas  escape 
through  the  stopcock.  When  no  more  gas  is  evolved, 
remove  and  clean  the  generator  thoroughly.  Mark  the 
level  of  the  water  inside  the  cylinder  with  a  rubber  band. 
Now  put  the  portion  which  has  been  heated  into 
the  generator  ;  fill  the  cylinder  afresh  with  water,  and 
collect  the  gas  given  off  when  10  c-c-  of  hydrochloric  acid 
are  run  in  upon  the  soda. 


Fig.    40 STOPCOCK    FUNNEL    GAS    GENERATOR 

AND  CYLINDER  USED  IN  ILLUSTRATING  THE  LAW 
OF  MULTIPLE    PROPORTIONS 


Experiments 


47 


Are  the  volumes  of  gas  in  the  two  cases  approxi- 
mately the  same?  Has  the  effect  of  the  heating  been 
to  expel  half  of  the  carbonic  acid  gas  contained  in  the 
baking  soda?  By  heating,  the  baking  soda  has  been 
converted  into  washing  soda.  How  much  greater  a 
volume  of  carbonic  acid  does  baking  soda  contain  than 
does  washing  soda?  How  do  your  results  verify  the 
law  in  question  ? 

NITROGEN  AND  ITS  HYDROGEN  COMPOUNDS 

EXPERIMENT  49.  Separation  of  Nitrogen  from 
the  Air.  Bend  the  wire  of  a  combustion  spoon  as 
showrn  in  Fig.  41,  and  fill  the  cup  with  red  phosphorus. 
Ignite  the  phos- 
phorus by  direct- 
ing a  Bunsen  flame 
down  upon  it,  and, 
resting  the  bend 
of  the  wire  on  the 
bottom  of  the 
pneumatic  trough, 
press  a  large, wide- 
mouthed  bottle 
over  it. 

Note  carefully 
how  the  phos- 
phorus burns. 
What  makes  it 
finally  go  out? 
What  becomes  of 
the  white  smoke 
at  first  formed  ? 
What  makes  the  water  rise  in  the  receiver?  Let  the 
apparatus  stand  until  the  fumes  have  completely  dis- 
appeared. Then  estimate  the  ratio  of  the  volume  of 


Fig.  41  APPARATUS   FOR   REMOVING   THE    OXYGEN 

FROM  A  CONFINED  PORTION  OF  AIR 


48  Elementary  Chemistry 

the  air  taken  to  the  volume  of  the  gas  left.  Close  the 
receiver  with  a  glass  plate  and  set  it  upright  upon  the 
table.  Move  the  plate  just  far  enough  to  one  side  to 
permit  the  entrance  of  a  blazing  splinter  of  wood. 
Does  it  continue  to  burn  ?  Is  nitrogen  combustible  ? 
Is  it  a  supporter  of  combustion  ? 

EXPERIMENT  50.  Nitrogen  by  the  Decomposition 
of  Ammonium  Nitrite.24  Mix  in  a  mortar  about  10^- 
(6cm-  circle)  of  ammonium  chlorid  with  about  i$ff-  of 
sodium  nitrite  and  place  the  mixture  in  a  flask  provided 
with  a  perforated  stopper  and  delivery  tube  (Fig.  16). 
Just  cover  the  mixture  with  water  and  heat  gently 
with  interposed  wire  gauze  until  the  reaction  begins ; 
then  remove  the  flame.  Collect  two  receivers  full  by 
water  displacement.  If  the  liquid  effervesces  too  much, 
cool  it  by  pouring  water  over  the  flask.  Reject  the 
first  bottle  full,  as  it  contains  the  air  which  was  in  the 
apparatus.  Remove  the  second  receiver  after  closing  it 
with  a  glass  slip  and,  holding  it  upside  down  (Why  ?), 
thrust  a  lighted  splinter  up  into  the  gas.  Is  nitrogen  a 
supporter  of  combustion  ?  Does  it  burn  ? 

NOTE  24.  Ammonium  Nitrite  Does  Not  Keep  Well.  Hence 
it  is  made  in  this  experiment  by  the  reaction  between  ammonium 
chlorid  and  sodium  nitrite.  The  heat  caused  by  the  reaction  is 
usually  sufficient  to  decompose  the  ammonium  nitrite  into  water 
and  nitrogen  as  soon  as  it  is  formed. 

EXPERIMENT  51.  Nitrogen  from  Potassium  Ni- 
trate by  Action  of  Iron  Powder.  Mix  well  io^-  ($cm. 
circle)  of  iron  powder  with  0.5  &•  (2  cm-  circle)  of  pow- 
dered potassium  nitrate,  put  the  mixture  in  a  hard  glass 
test  tube,  fitted  with  a  cork  and  delivery  tube  (Fig.  34), 
and  apply  heat.  Be  careful  to  heat  very  gradually,  as 
the  reaction  may  become  rather  violent.  Collect  sam- 
ples of  the  gas  by  water  displacement,  and  test  them 
with  a  blazing  splinter. 


Experiments  49 

EXPERIMENT  52.  Ammonia  from  Ammonium  Salts 
by  Action  of  Caustic  Alkalis  or  Lime.  Cover  a  pinch 
of  ammonium  chlorid  or  nitrate  in  a  test  tube  with  po- 
tassium or  sodium  hydroxid  (caustic  potash  or  soda) 
solution.  Heat  gently  to  boiling  and  cautiously  observe 
odor  by  wafting  the  air  above  the  mouth  of  the  test 
tube  against  the  nostrils.  Put  a  strip  of  moistened  pink 
litmus  paper25  across  the  mouth  of  the  test  tube  and 
note  any  change  of  color. 

Put  a  little  slaked  lime2  6  in  the  palm  of  one  hand  and 
a  little  ammonium  chlorid  or  nitrate  in  the  other.  Smell 
of  each  substance.  Then  rub  the  substances  together 
between  the  palms  and  smell  again.  Also  touch  the 
mixture  with  a  strip  of  moist  pink  litmus  paper25. 

•  NOTE  25.  Pink  Litmus  Paper.  To  make  litmus  paper  of  a 
pink  color,  put  a  few  drops  of  dilute  hydrochloric  acid  in  a  watch 
glass  or  on  a  piece  of  glass,  and  draw  the  strip  of  paper  through 
it.  Wash  out  the  excess  of  the  acid  by  holding  the  paper  in  a 
stream  of  water  from  the  hydrant.  The  blue  color  may  be  restored 
by  using  ammonium  hydroxid  instead  of  hydrochloric  acid.  As 
litmus  paper  is  usually  sold  with  its  color  intermediate  between 

Eink  and  blue,  it  is  a  good  practice  to  treat  it  as  above  so  as  to 
ave  it  of  a  decided  blue  or  pink  color  before  making  a  test. 

NOTE  26.  Use  Freshly  Slaked  Lime.  The  lime  must  be 
freshly  slaked.  "Air-slaked  "  lime  generally  will  not  do. 

EXPERIMENT  53.  Ammonia  from  the  Destructive 
Distillation  of  Some  Animal  Substances.  Heat  some 
such  substance  as  gelatin,  glue,  hair,  or  feathers  in  a 
test  tube  with  a  moistened  strip  of  pink  litmus  paper 
held  across  its  mouth.  What  products,  solid,  liquid, 
and  gaseous,  are  formed  ? 

EXPERIMENT  54.  Preparation  and  Properties  of 
Ammonia.  Arrange  an  apparatus  as  shown  in  Fig.  42. 
Put  about  25  #•  (ycm.  circle)  ammonium  chlorid  and 
about  three  times  its  bulk  of  slaked  lime26  in  the 
flask,  and  add  just  enough  water  to  make  a  pasty  mass ; 
or,  fill  the  flask  about  a  third  full  of  strong  ammonia 


elementary  Chemistry 


Fig.  42 APPARATUS  FOR  PREPARING  AMMONIA 

water  (ammonium  hydroxid).  The  rim  of  the  funnel 
should  dip  just  below  the  surface  of  the  water  in  the 
dish.  Heat  very  gently,  and  as  soon  as  the  gas  evolved 
is  nearly  all  absorbed  by  the  water,  substitute  for  the 
funnel  a  straight  glass  tube.  Insert  this  delivery  tube 
into  a  narrow-mouthed  bottle  and  collect  the  bottle  full 
of  the  gas  by  upward  displacement27. 

Keeping  the  receiver  always  upside  down  (Why?), 
cork  it  tightly  (or  cover  it  with  a  greased  glass  plate)  and 
set  it  aside  in  an  inverted  position.  Collect  in  like  man- 
ner a  second  bottle  full  of  the  gas.  Dip  a  glass  rod  into 
strong  hydrochloric  acid  and  bring  the  adherent  drop 
just  above  the  jet  of  gas.  What  occurs  ?  Replace  the  fun- 
nel and  continue  to  absorb  the  gas  as  long  as  it  can  be 
made  to  come  off.  The  solution  is  ammonium  hydroxid. 

Hold  the  neck  of  the  first  receiver  under  water  and 
remove  the  cork.  Does  it  seem  to  stick  in  the  neck  ? 
If  so,  why  ?  What  makes  the  water  rush  up  into  the 
bottle  ?  Test  the  water  in  the  bottle  with  pink  litmus 


Experiments  5 1 

paper25.  Hold  the  second  receiver  upside  down,  re- 
move the  cork  and  insert  a  lighted  splinter  of  wood. 
Does  ammonia  support  combustion  ?  Does  it  burn  ? 

To  a  little  of  the  ammonium  hydroxid  add  a  few 
drops  of  Nessler's  reagent.  Also  test  a  little  with  solu- 
tions of  iron  chlorid,  ferrous  sulfate,  aluminum  chlorid 
or  sulfate,  and  copper  sulfate  (at  first  very  little,  and 
then  an  excess).  Put  a  little  ammonium  hydroxid  in  a 
small  test  tube  and  boil  for  a  few  seconds  so  as  to  fill 
the  tube  with  ammonia.  Then  rapidly  invert  it  in  a 
beaker  filled  with  very  dilute  copper  sulfate  solution. 
What  happens,  especially  in  change  of  color  ? 

NOTE  27.  Collecting  a  Gas  by  Upward  Displacement.  When 
a  gas  is  soluble  in  water  it  cannot  of  course  be  collected  by  water 
displacement.  If  the  gas  is  lighter  than  air,  it  can  be  collected  by 
delivering  it  into  an  inverted  receiver  ;  the  delivery  tube  should 
be  thrust  as  high  up  as  possible,  so  that  the  lighter  gas  may  push 
the  air  down  and  out  of  the  receiver. 

EXPERIMENT  55.  Ammonia  by  the  Interaction  of 
Potassium  Nitrate,  Potassium  Hydroxid,  and  Iron 
Powder.  Mix  together  0.5^-  (2  cm-  circle)  of  potassium 
nitrate,  0.3^-  (6mm-  circle)  of  potassium  hydroxid,  and  25^- 
(5  cm.  circle)  of  iron  powder,  put  the  mixture  in  a  hard 
glass  test  tube  and  heat  gently.  How  can  you  prove 
that  ammonia  is  given  off  ?  What  is  the  gaseous  product 
of  heating  a  mixture  of  potassium  nitrate  and  iron  pow- 
der (Experiment  51)?  What  of  heating  a  mixture  of 
potassium  hydroxid  and  aluminum  powder  (Experiment 
26)  ?  Zinc  or  aluminum  powder  would  also  answer. 

CARBON 

EXPERIMENT  56.  Formation  of  Charcoal.  Place  in 
a  small  Hessian  crucible  or  tin- box  cover  a  thin  layer 
of  sand  and  place  upon  it  a  small  piece  of  soft  wood 
and  of  hard  wood,  a  fragment  of  bone,  and  a  lump  of 
starch.  Cover  them  with  a  thick  layer  of  sand  and 


Elementary  Chemistry 


heat  very  hot  for  at  least  twenty  minutes.  Pour  off  the 
sand  and  compare  the  products.  What  conclusions  can 
you  draw  as  to  the  distribution  of  carbon  ?  What  was 
the  purpose  of  imbedding  the  objects  in  sand  ? 

EXPERIMENT  57.  Graphite  from  Pig  Iron.  Put 
about  3^-  (2  cm-  circle)  of  borings  of  foundry  pig  iron  in  a 

beaker  and  add  iooc-c- 
of  dilute  nitric  acid 
(made  by  mixing  ioc-c- 
of  the  concentrated 
acid  with  go  c-c-  of 
water).  Boil  gently 
(Fig.  43),  replacing 
from  time  to  time 
the  water  which  has 
boiled  away,  until  the 
residue  does  not  seem 
gritty  when  rubbed 
with  a  glass  rod.  Fil- 
ter and  wash  the  resi- 
due and  let  it  dry. 
Compare  its  proper- 
ties with  those  of  sam- 
ples of  graphite  that 
you  can  obtain  from 
different  sources. 
EXPERIMENT  58.  Preparation  of  Lampblack.  Put 
a  lump  (2  mm,}  of  rosin  in  a  spoon  or  tin-box  cover  and 
set  fire  to  it.  Hold  the  rounded  end  of  a  test  tube  filled 
with  cold  water  in  the  flame.  Examine  the  deposit  on 
the  tube.  Why  was  the  tube  filled  with  cold  water? 

EXPERIMENT  59.  Density  and  Porosity  of  Char- 
coal. Put  a  piece  of  charcoal  in  a  test  tube  half  full 
of  water.  Does  the  charcoal  seem  lighter  or  heavier 
than  water  ?  Boil  the  water  for  several  minutes.  What 


Fig.   43 BOILING  A  LIQUID  IN  A  BEAKER 


Experiments  5  3 

is  observed  on  the  surface  of  the  charcoal  ?  Let  the 
water  cool  with  the  charcoal  in  it,  and  look  at  it  from 
time  to  time.  What  is  your  final  conclusion  as  to  the 
density  of  charcoal  ?  Do  not  draw  this  conclusion  until 
the  charcoal  has  been  in  the  water  for  some  time. 
Account  for  its  behavior  before  and  after  boiling. 

With  the  aid  of  tongs  hold  a  piece  of  charcoal  in  a 
Bunsen  flame  until  it  is  red  hot,  and  then  drop  it  into 
water.  Wait  until  it  sinks.  Explain  its  sinking. 

EXPERIMENT  60.  Adsorption  of  Gases  by  Char- 
coal. Fill  a  large  test  tube  half  full  of  wrater  and  add 
to  it,  drop  by  drop,  ammonium  hydroxid,  so  as  to  give 
it  a  faintly  perceptible  smell.  You  should  just  be  able 
to  smell  the  ammonia  when,  after  shaking  up  the  liquid, 
the  mouth  of  the  test  tube  is  put  under  the  nostrils. 
Heat  some  finely  powdered  charcoal  in  an  evaporating 
dish  nearly  to  redness,  let  it  cool,  and  pour  it  into  the 
weak  ammonia  water.  Shake  well  for  a  minute  or  so, 
and  then  apply  the  tube  to  the  nostrils.  Has  the  smell 
of  ammonia  been  diminished  ?  What  was  the  purpose 
of  heating  the  charcoal  beforehand  ? 

EXPERIMENT  61.  Reduction  by  Charcoal.  Put  a 
pinch  of  finely  powdered  charcoal  in  a  small  test  tube, 
a  pinch  of  powdered  copper  oxid  in  a  second  test  tube, 
and  a  few  bits  of  copper  wire  or  granulated  copper  in 
a  third  tube.  Fill  each  tube  about  a  fifth  full  of  dilute 
nitric  acid  and  shake  well.  Note  any  action  that  may 
take  place,  such  as  effervescence,  colored  fumes  or  liquid. 
Place  the  test  tubes  side  by  side  in  a  beaker  about 
half  full  of  water,  and  heat  the  water  until  it  is  so  hot 
that  you  can  hardly  bear  your  hand  in  it.  Note  now 
any  changes  or  reactions  in  the  test  tubes.  Are  the 
differences  in  the  behavior  of  the  three  solids  when 
placed  in  nitric  acid  sufficient  to  characterize  them  ? 
In  other  words,  is  this  "nitric  acid  test"  decisive? 


54  Elementary  Chemistry 

Mix  well  in  a  mortar  4^-  ($cm'  circle)  of  copper  oxid 
with  2ff-  (4cm-  circle)  of  powdered  charcoal.  Place  the 
mixture  in  a  test  tube  and  heat  as  hot  as  possible  with- 
out melting  the  glass  for  at  least  five  minutes.  Does 
the  color  of  the  mixture  change  ?  If  so,  what  substance 
may  it  indicate  the  presence  of  ?  Put  a  pinch  of  the 
product  in  a  small  test  tube  and  add  nitric  acid  as  above. 
Is  there  any  evidence  that  copper  has  been  formed  and 
is  present?  What  role  does  the  charcoal  play? 

EXPERIMENT  62.  Decolorizing  Action  of  Bone- 
black.  Into  a  test  tube  nearly  full  of  water  put  enough 
molasses  or  litmus  solution  to  tinge  the  water  slightly. 
Fit  a  funnel  with  a  filter  paper  and  nearly  fill  it  with 
boneblack.  Pour  the  mixture  prepared  upon  the  bone- 
black  and  catch  the  filtrate  in  a  second  test  tube.  If 
the  filtrate  is  not  perfectly  colorless,  pour  it  upon  the 
boneblack  again,  and  continue  this  until  all  the  color  is 
removed  from  the  mixture. 

EXPERIMENT  63.  Combustibility  of  Different 
Forms  of  Carbon.  Place  a  wire  gauze  on  a  ring  of  a 
stand  at  such  a  height  above  a  Bunsen  flame  that  a 
circle  about  3 cm-  in  diameter  is  made  red  hot.  Place  in 
this  circle  pieces  "($mm-)  of  graphite  (from  a  "lead  pen- 
cil "),  of  charcoal,  of  gas  carbon,  of  soft  and  of  hard  coal, 
and  heat  until  the  charcoal  changes  into  ash  ;  be  care- 
ful to  have  all  the  substances  equally  heated.  Describe 
fully  the  changes  which  each  substance  undergoes. 

THE  COMPOUNDS  OF  CARBON  WITH  OXYGEN 

EXPERIMENT  64.  Carbon  Dioxid  a  Product  of  Com- 
bustion. Drop  a  piece  of  burning  paper  into  a  dry,  wide- 
mouthed  bottle  and  cover  it  with  a  glass  slip.  When  the 
paper  ceases  to  burn,  pour  in  some  lime  water  and  shake 
the  contents  of  the  bottle  vigorously.  What  happens 
to  the  lime  water  ? 


Experiments 


55 


EXPERIMENT  65.  Carbon  Dioxid  Given  off  in  Res- 
piration. Fill  a  large  test  tube  a  third  full  of  lime  water, 
and  by  means  of  a  glass  tube  make  the  breath  bubble 
through  the  solution  a  dozen  or  so  times.  What  occurs  ? 

EXPERIMENT  66.  Carbon  Dioxid  Produced  by 
Fermentation.  Dissolve  a  handful  of  brown  sugar  or 
an  equal  bulk  of  molasses  in  about  a  liter  of  water  con- 
tained in  a  bottle  or  flask  provided  with  a  delivery 
tube.  Add  a  little  yeast  and  set  the  apparatus  in  a 
warm  place  (30°  to  40°).  Collect  the  gas  which  soon 
begins  to  form  in  test  tubes  and  test  it  with  lime  water. 


Fig.  44 GENERATING   A    GAS   AND   COLLECTING  IT  BY  DOWNWARD  DISPLACEMENT 

EXPERIMENT  67.  Carbon  Dioxid  from  a  Carbonate 
by  Action  of  an  Acid.  Place  several  lumps  of  marble 
(calcium  carbonate)  in  a  gas  generator  and  cover  them 
with  water.  Connect  with  a  wash  bottle  a  fourth  full 
of  water  (Fig.  44).  Pour  some  strong  hydrochloric  acid 
down  the  funnel  so  as  to  cause  a  brisk  evolution  of  gas. 
Collect  the  gas  by  placing  the  delivery  tube  at  the 


56  Elementary  C lie  mist  ry 

bottom  of  a  receiver.  Carbon  dioxid  is  heavier  than 
air  and  collects  at  the  bottom  of  the  receiver.  This 
method  of  collecting  a  gas  is  known  as  that  of  "down- 
ward displacement."  Collect  five  receivers  full  for  use 
in  Experiment  68,  and  close  them  with  glass  slips. 

EXPERIMENT  68.  Properties  of  Carbon  Dioxid. 
Lower  a  lighted  splinter  of  wood  into  a  receiver  of  car- 
bon dioxid.  What  happens  ?  Pour  a  little  lime  water 
into  another  receiver  of  the  gas  and  shake  it  up.  What 
happens  ?  Pour  a  receiver  full  of  carbon  dioxid  as  you 
would  a  receiver  of  water  into  a  second  receiver  con- 
taining only  air.  Lower  a  lighted  splinter  into  the 
second  receiver.  What  evidence  is  there  that  the  gas 
has  been  poured  from  the  one  receiver  into  the  other  ? 
Empty  just  as  if  the  carbon  dioxid  were  water  a  receiver 
full  of  carbon  dioxid  upon  a  candle  flame.  What  hap- 
pens ?  Holding  one  end  of  a  bit  of  magnesium  ribbon 
by  means  of  tongs,  ignite  the  other  end  thoroughly, 
and  plunge  it  into  a  large  receiver  full  of  the  gas. 
What  are  the  black  and  the  white  particles  formed  ? 

EXPERIMENT  69.  Action  of  Carbon  Dioxid  on 
Litmus.  Add  a  few  drops  of  litmus  solution  to  water 
in  a  test  tube  and  pass  carbon  dioxid  into  it  for  a  few 
minutes.  What  change  of  color  ? 

EXPERIMENT  70.  Carbon  Dioxid  Absorbed  by 
Sodium  or  Potassium  Hydroxid  Solutions.  Pass 
carbon  dioxid  into  a  solution  of  caustic  potash  or  soda 
(potassium  or  sodium  hydroxid  solution).  When  the 
gas  ceases  to  be  absorbed,  pour  a  little  of  the  solution 
into  a  test  tube  and  add  dilute  hydrochloric  acid.  What 
does  the  effervescence  that  ensues  go  to  show  ?  Pour 
the  rest  of  the  solution  into  a  shallow  dish  and  let  it 
stand  until  crystals  appear.  Place  some  of  these  crys- 
tals in  a  test  tube  and  add  hydrochloric  acid.  What  evi- 
dence is  there  that  the  crystalline  mass  is  a  carbonate? 


Experiments 


57 


EXPERIMENT  71.  Carbon  Dioxid  in  Solution  Dis- 
solves Calcium  Carbonate.  Mix  lime  water  with  an 
equal  volume  of  water  in  a  test  tube  and  pass  carbon 
dioxid,  purified  by  passing  it  through  water  in  a  wash 
bottle  (Fig.  44),  through  it  for  some  time.  Does  the 
white  precipitate  of  calcium  carbonate  finally  dissolve.? 
Boil  some  of  this  clear  solution  so  as  to  expel  the  car- 
bon dioxid  from  solution.  What  happens  ? 

EXPERIMENT  72.  Carbon  Monoxid  by  Action  of 
Sulfuric  Acid  on  Sodium  Formate.  Fit  a  test  tube 
with  a  perforated  cork  through 
which  passes  a  short,  straight 
piece  of  glass  tubing  ending 
in  a  jet  (Fig.  45).  Put  enough 
sodium  formate  in  the  tube 
to  fill  it  to  the  depth  of  about 
a  centimeter,  and  cover  it  to 
a  depth  of  about  4cm-  with 
strong  sulfuric  acid.  Hold- 
ing the  tube  with  a  test  tube 
holder,  warm  it  cautiously  so 
that  the  contents  may  not 
froth  over,  and  light  the  gas 
given  off.  What  is  the  appear- 
ance of  the  flame  just  as  soon 
as  the  gas  is  lighted  and  be- 


fore   the    glass    tip    has    been      Fig.  45- PREPARING  CARBON  MON- 

heated   red   hot?      Be   very 

careful  not  to  let  the  poisonous  gas  escape  into  the 
room,  repeatedly  applying  a  light  to  the  jet  tube  so  as 
to  burn  the  gas  as  soon  as  formed. 

P^XPERIMENT  73.  Carbon  Monoxid  by  the  Action  of 
Sulfuric  Acid  on  Potassium  Ferrocyanid.  Put  about 
io£--  (5  cm.  circle)  of  potassium  ferrocyanid  in  a  flask  (200 
to  300  c-c-)  provided  with  a  delivery  tube  ending  in  a  jet, 


Elementary  Chemistry 


and  add  about  50^-  of  strong  sulfuric  acid.  Heat 
gently  (Fig.  46)  and  ignite  the  escaping  gas  ;  note  the 
appearance  of  the  flame  and  any  other  phenomena  that 

you  may  observe. 

EXPERIMENT  74.  Oxids  of 
Carbon  from  Oxalic  Acid. 
Into  a  flask  (200  to  300 c-c-) 
fitted  with  a  delivery  tube  put 
about  5^-  (4««-  circle)  of  solid 
oxalic  acid  and  add  about 
40^-  of  strong  sulfuric  acid. 
Heat  cautiously  and  after  the 
air  has  all  been  Driven  out  of 
the  apparatus,  collect  by  water 
displacement  a  long,  narrow 
test  tube  full  of  the  gas.  Close 
the  tube  with  the  thumb  un- 
der water  and  transfer  it  to  a 
beaker  nearly  full  of  a  very 
dilute  solution  of  caustic  soda 
or  potash.  Let  it  stand  until 
the  liquid  ceases  to  rise  in  the  tube.  What  is  the  decrease 
in  volume  due  to  ?  What  is  the  ratio  of  the  volume  of 
the  two  oxids  of  carbon  obtained  from  oxalic  acid  ? 

EXPERIMENT  75.  (Quantitative.)  To  Find  the 
Weight  of  a  Liter  of  Carbon  Dioxid.  Fit  a  flask 
(300  to  400  c-c-)  with  a  one-hole  rubber  stopper  through 
which  passes  a  glass  tube  a  little  longer  than  the  flask, 
over  one  end  of  which  is  slipped  a  bit  of  rubber  tubing 
(Fig.  47).  Fill  the  flask  brimming  full  of  cold  water, 
and  insert  the  stopper  and  tube;  be  careful  to  exclude 
all  air  bubbles  and  to  have  the  water  reach  to  the  end 
of  the  rubber  tip.  Close  the  rubber  tube  as  near  to  the 
glass  as  possible  with  a  pinchcock,  and  mark  with  a 
pencil  a  line  around  the  stopper  even  with  the  rim  of 


Fig.  46 PREPARING  CARBON  MON- 

OXID     FROM     POTASSIUM     FERROCY- 
ANID 


Experiments 


59 


the  flask's  neck.  Weigh  to  decigrams  the  flask  thus 
filled  with  water  ;  this  weight  in  grams  is  equal  to  the 
volume  in  cubic  centimeters. 

Empty  out  the  water  and  dry  the  apparatus  thor- 
oughly. Multiply  the  volume  by  0.001293  (the  weight 
of  i  c-c-  of  air  at  standard  conditions)  to  get  the  weight 
of  air  filling  the  flask  at  standard  conditions.  Open  the 
pinchcock  and  connect  the  rubber  tubing  with  a  cur- 
rent of  dry  carbon  dioxid.  Loosen  the  stopper  so  that 
the  carbon  dioxid  delivered  at  the  bottom  of  the  flask 
can  drive  out  the  air.  After  about  five  minutes  insert 
the  stopper  to  the  same  extent  as  before,  i.  c.,  to  the 
pencil  line,  close  the  pinchcock,  and  disconnect  from 
the  carbon  dioxid  generator.  Open  the  pinchcock  for 
an  instant  so  as  to  let  the  ex- 
cess of  carbon  dioxid  escape, 
and  weigh  the  apparatus  to 
centigrams.  Read  the  ther- 
mometer and  the  barometer. 

Repeat  the  operation  of 
filling  the  flask  with  carbon 
dioxid  so  as  to  make  sure  that 
all  the  air  has  been  expelled ; 
this  will  be  shown  by  no  in- 
crease in  weight  in  the  second 
weighing.  As  soon  as  a  con- 
stant weight  has  been  attained, 
again  read  the  thermometer 
and  barometer,  using  the  last 
readings  for  the  calculations. 
The  difference  of  the  weights 
of  the  flask  full  of  air  and  filled  with  carbon  dioxid,  plus 
the  calculated  weight  of  the  air,  gives  the  weight  of  the 
carbon  dioxid.  Reduce  this  volume  to  o°  and  j6omm-, 
and  then  compute  the  weight  of  a  liter  of  carbon  dioxid. 


Fig.  47  —  APPARATUS  FOR  FINDING 

THE  WEIGHT  OF  A  LITER  OF  CARBON 

DIOXID 


6o 


Elementary  Chemistry 


SOME    NITROGEN  AND   HYDROGEN  COMPOUNDS 
OF    CARBON 

EXPERIMENT  76.  Methane  from  Sodium  Acetate 
by  Action  of  Soda-lime.  Pulverize  about  10^-  of  fused 
and  dry  sodium  acetate  and  mix  it  thoroughly  in  a  mortar 
with  an  equal  weight  of  fused  and  dry  soda-lime.  Heat 

the  mixture  in  a 
flask  ( 100  to  2ooc-c-) 
provided  with  a 
one-hole  cork,  de- 
livery tube  and  a 
safety  bottle28 
(Fig.  48),  and  col- 
lect a  couple  of 
receivers  full  by 
water  displace- 
ment. Ascertain 
whether  the  gas  is 
combustible  or  a 
supporter  of  com- 
bustion. Pour  a  little  lime  water  into  one  of  the 
receivers  just  after  the  methane  has  been  ignited.  The 
result  proves  what  element  to  be  present  in  methane  ? 
How  could  you  prove  the  presence  of  hydrogen  in  it  ? 
EXPERIMENT  77.  Ethylene  from  Alcohol  by  Ac- 
tion of  Sulfuric  Acid.  Pour  10^-  of  water  into  a 
flask  (200  to  3ooc-<;-),  add  slowly  with  constant  stirring 
30  c-c-  of  strong  sulfuric  acid,  and  cool  the  flask  by  hold- 
ing it  under  cold  water.  Then  add  ioc-c-  of  alcohol.  Fit 
a  cork  and  delivery  tube  to  the  flask,  interpose  a  safety 
bottle28  (Fig.  48),  heat  gently,  and  collect  a  couple  of 
receivers  full  of  the  gas  by  water  displacement.  Note 
its  odor.  How  does  it  burn  ?  Compare  its  flame  with 
those  of  the  other  combustible  gases  thus  far  studied. 


Fig.  48 APPARATUS  FOR  GENERATING  A   GAS  TO 

COLLECTED   BY  WATER  DISPLACEMENT 


Experiments  61 

NOTE  28.  Safety  Bottle.  The  object  of  the  safety  bottle  is  to 
prevent  any  water  which  may  be  drawn  back  through  the  delivery 
tube  from  entering  the  hot  flask  and  probably  breaking  it.  The 
entrance  and  exit  tubes  of  a  safety  bottle  should  not  project  much 
below  the  lower  surface  of  the  cork. 

EXPERIMENT  78.  Acetylene  by  Action  of  Water 
on  Calcium  Carbid.  Place  a  few  small  lumps  of  cal- 
cium carbid  in  a  gas  generator,  and  cover  them  with 
strong  alcohol.  Slowly  add  water  through  the  funnel 
tube  so  as  to  cause  a  brisk  evolution  of  the  gas.  Catch 
a  couple  of  receivers  full  and  ascertain  its  physical 
properties.  With  what  kind  of  a  flame  does  it  burn  ? 

EXPERIMENT  79.  Destructive  Distillation.  Fill  a 
test  tube  to  a  depth  of  about  3 cm-  with  excelsior  or  soft 
coal,  packing  it  in  tight,  and  support  the  tube  horizon- 
tally between  two  rings  of  a  retort  stand  (Fig.  34).  Fit 
in  a  cork  and  delivery  tube,  and  heat  the  lower  end  of 
the  tube,  gently  at  first,  but  finally  as  hot  as  possible 
without  melting  the  glass.  Let  the  delivery  tube  dip 
below  the  surface  of  the  water  in  a  pneumatic  trough, 
and  from  time  to  time  catch  a  test  tube  full  of  the  gas 
given  off,  and  test  its  inflammability.  When  no  more 
gas  is  evolved,  remove  the  delivery  tube  from  the 
water.  Test  the  liquid  which  has  collected  in  the  tube 
near  its  mouth  with  blue  litmus  paper.  What  effect  ? 
What  are  the  physical  properties  of  the  residue  ? 

EXPERIMENT  80.  A  Simple  Gas  Factory.  Roll  a 
piece  of  paper  (foolscap  size)  so  as  to  form  a  cone  with 
one  end  about  0.5 cm-  in  diameter  and  the  other  2  to  3 cm- 
in  diameter.  Hold  it  vertically  with  the  narrow  end 
up  and  set  fire  to  the  other  end.  Apply  a  flame  to  the 
upper  end  a  little  above  the  paper.  Does  the  escaping 
gas  catch  fire  ?  When  the  paper  has  burned  about  a 
third  of  its  length,  quench  the  flame  by  dipping  it  under 
water.  Unroll  the  paper  and  examine  any  deposit  on 
that  part  of  it  which  formed  the  lining  of  the  cone. 


62 


Elementary  Chemistry 


EXPERIMENT  81.     A  Candle   as   a   Gas  Factory. 

Heat  a  small  bit  of  a  candle  in  an  old  test  tube  until 
vapors  are  formed  that,  on  escaping  from  the  tube, 
may  be  ignited.  Blow  out  a  candle  flame  and  imme- 
diately bring  a  burning  match  or 
flame  down  towards  the  wick. 
What  evidence  is  there  to  show 
that  a  gas  is  being  given  off  ? 

THE  ATMOSPHERE 

EXPERIMENT £2.  (Quantitative^) 
To  Determine  the  Percentage 
of  Oxygen  in  the  Air.  Fill  a 
hydrometer  jar  nearly  full  of  water 
at  the  temperature  of  the  room. 
Pour  a  little  water  in  a  graduated 
tube,  place  its  open  end  in  the 
water  in  the  hydrometer  jar,  and 
let  in  air,  if  necessary,  by  raising  it 
up  until  it  nearly  fills  the  gradu- 
ated portion.  Lift  the  tube  up 
until  the  level  of  the  water  within 
and  without  is  the  same  and  read 
off  the  volume  of  the  air.  Note 
the  temperature  of  the  water  and 
the  reading  of  the  barometer,  and 
reduce  the  volume  read  to  stand- 
ard conditions.  Bend  a  copper  wire 
about  twice  as  long  as  the  graduated  tube  (Fig.  49)  in  a 
V-shape,  sharpen  one  end  with  a  file,  and  stick  on  this 
pointed  end  a  piece  of  phosphorus  which  has  just  been 
scraped  clean  under  water.  Immerse  the  phosphorus 
on  the  end  of  the  wire  under  the  water  in  the  jar,  and 
bring  the  tube  down  over  it  so  that  the  phosphorus  pro- 
jects up  into  the  air.  What  happens? 


Fig.  49  —  DETERMINING  THE 

PERCENTAGE       OF       OXYGEN 

IN    THE    AIR 


Experiments  63 

Let  the  apparatus  stand  for  at  least  twenty-four 
hours,  then  lift  the  tube  up  until  the  level  of  the  water 
inside  and  out  is  the  same  and  the  phosphorus  is  under 
water,  and  read  off  the  volume.  Reduce  this  volume  to 
standard  conditions  after  reading  the  temperature  and 
pressure.  Remove  the  phosphorus  and  again  scrape  it 
clean  under  water  and  replace  it  in  the  tube  as  before, 
leaving  it  there  until  the  next  day.  Again  find  the  vol- 
ume of  the  gas,  reduce  it  to  standard  conditions,  and  see 
if  it  is  the  same  as  before.  Compute  the  percentage  of 
oxygen  in  the  sample  of  air  taken. 


O         1          234567 

Fig.    50 TEST    TUBE    AND    SCALE    FOR     DETERMINING    THE    VOLUME    OF    OXYGEN 

IN    A    GIVEN    VOLUME    OF    AIR 

EXPERIMENT  83.     The  Volume  of  Oxygen  in  Air. 

Select  a  long,  narrow  test  tube  and  cut  a  piece  of  paper 
whose  length  has  the  same  ratio  to  that  of  the  test  tube 
as  the  scale  has  to  the  test  tube  in  the  figure  (Fig.  50). 
Bend  the  ends  of  the  strip  of  paper  together  and  crease 
it  in  the  middle,  and  do  this  a  second  and  a  third  time. 
Then  straighten  the  paper  out  so  as  to  form  a  scale  of 
eight  equal  divisions  to  serve  as  a  measure  of  the  vol- 
ume of  the  test  tube.  Instead  of  the  above,  any  rule 
or  scale  may  be  used. 

Fill  the  test  tube  about  one-eighth  full  of  dry  pyro- 
gallic  acid,  and,  holding  the  test  tube  so  that  the  thumb 
may  be  three-eighths  of  the  distance  from  the  bottom, 
pour  in  potassium  hydroxid  solution  up  to  the  level  of 
the  thumb.  Immediately  close  the  tube  with  the 
thumb  and  shake  the  air  and  solution  well  together  for 


64  Elementary  Chemistry 

several  minutes.  Open  the  test  tube  with  the  thumb 
under  water  in  a  pneumatic  trough  (a  beaker  will  do) 
and  let  stand  for  a  few  minutes  so  that  the  air  may 
come  to  the  temperature  of  the  room.  By  means  of 
the  scale  measure  the  volume  of  the  gas  left  in  the 
test  tube,  lifting  it  up  so  that  the  level  of  the  water 
inside  and  out  may  be  the  same.  How  many  volumes 
of  air  did  you  take  ?  How  many  volumes  of  gas  have 
you  now?  How  many  volumes  of  oxygen  were  ab- 
sorbed ?  What  is  the  volumetric  composition  of  air  ? 
EXPERIMENT  84.  Action  of  Dust  on  the  Precipita- 
tion of  Water  Vapor.  Fit  a  bottle  (500  to  2,000 c-c-} 
with  a  two-hole  rubber  stopper,  through  each  of  the 
holes  of  which  passes  an  L-tube  which  is  connected 
with  a  chlorid  of  calcium  tube.  To  one  of  the  calcium 
chlorid  tubes  is  attached  a  small  bicycle  pump  or  a 
rubber  bulb  with  a  valve.  Put  enough  water  in  the 
bottle  to  fill  it  to  a  depth  of  about  2  cm-.  Insert  the  stop- 
pers tightly  and,  closing  with  the  thumb  one  end  of 
the  calcium  chlorid  tube  not  connected  with  the  pump, 
pump  air  in  through  the  other.  When  the  pressure  has 
become  rather  great,  suddenly  remove  the  thumb  and 
note  what  takes  place  in  the  bottle.  Repeat  several 
times  so  as  to  make  sure  of  the  appearance  of  the  phe- 
nomenon. Fill  the  calcium  chlorid  tubes  loosely  with 
cotton  wool  and  pump  in  air  as  before.  Do  this  a  num- 
ber of  times  so  as  to  replace  the  air  in  the  bottle  with 
air  which  has  been  freed  from  its  dust  particles  by 
filtration  through  cotton.  Is  there  any  change  in  the 
phenomenon  ?  Let  the  bottle  stand  for  several  hours 
and  then  pump  filtered  air  into  it.  What  happens  ? 
Let  it  stand  for  several  hours  longer  and  then  do  as 
before.  Now  thrust  a  lighted  match  for  an  instant  into 
the  neck  of  the  bottle  (after  loosening  the  stopper)  so 
as  to  introduce  some  smoke,  i.  e.,  dust,  into  the  bottle, 


Experiments  65 

and  pump  in  filtered  air.  What  happens  ?  What  con- 
clusion can  be  drawn  as  to  the  action  of  dust  particles 
in  the  formation  of  water  drops  from  vapor  ? 

EXPERIMENT  85.  (Quantitative^]  To  Find  the 
Weight  of  a  Liter  of  Air.  Melt  off  the  top  of  one 
tomato  can  and  the  bottom  of  another.  Pierce  a  hole 
about  3 mm-  in  diameter  in  the  center  of  the  bottom 
melted  off  and  solder  over  it  a  bicycle  valve.1 

Solder  this  bottom  on  the  can,  the  top  of  which  was 
removed.  Connect  with  a  bicycle  pump,  and  pump  in 
air  until  the  pump  works  very  hard.  Disconnect  the 
pump  and  weigh  the  can  to  centigrams. 

Slip  over  the  valve  a  piece  of  rubber  tubing  in  which 
has  been  placed  a  match  with  its  head  removed.  Con- 
nect the  other  end  of  the  tubing  with  an  aspirating 
bottle,  being  sure  to  have  the  pressure  in  the  bottle 
equal  to  that  of  the  atmosphere.  Pinch  the  rubber 
tubing  around  the  match  which  should  be  resting  in 
the  valve,  and,  pressing  the  match  against  the  valve, 
open  it  a  little  so  as  to  let  some  of  the  air  escape.  Con- 
tinue doing  this  until  no  more  air  escapes  from  the  can. 
As  the  air  on  expanding  cools,  wait  a  few  minutes  and 
then  open  the  valve  again,  having  the  vessel  employed 
to  catch  the  water  driven  out  of  the  aspirator  at  such  a 
height  that  the  water  levels  are  the  same.  Remove 
the  can  and  weigh  it.  The  loss  in  weight  represents 
the  weight  of  the  volume  of  air  which  has  escaped 
from  the  can. 

Measure  the  volume  of  this  water  expelled  from  the 
aspirator  either  by  weighing  to  decigrams  or  by  means 
of  graduates.  Reduce  the  volume  to  o°  and  760 mm-. 
Calculate  the  weight  of  one  liter  of  air. 


JThis  valve  must  close  perfectly  air-tight  even  when  the  screw- 
cap  is  not  placed  on  it. 


66  Elementary  Chemistry 

FIRE   AND   FLAME 

EXPERIMENT  86.     Kindling  Temperature.     I.    Put 

a  few  drops  of  carbon  bisulfid  into  a  beaker  and  cover 
it  with  a  card  or  glass  slip.  The  vapor  of  the  liquid 
then  mixes  with  the  air  in  the  beaker.  Heat  the  end 
of  a  glass  rod  to  redness  and  thrust  it  into  the  beaker. 
Be  careful  to  have  your  face  as  far  as  possible  from  the 
beaker.  Repeat,  using  alcohol  instead  of  carbon  bisul- 
fid. What  are  your  conclusions  in  regard  to  the  tem- 
peratures at  which  different  C9mbustibles  take  fire  ? 

II.  Try  to  ignite  illuminating  gas  with  a  spark  (not 
a  flame)  at  the  end  of  a  match  stick.  Is  the  tempera- 
ture of  the  spark  high  enough  ?  Press  a  piece  of  wire 
gauze,  held  horizontally,  down  upon  a  Bunsen  flame. 
Give  reasons  for  what  you  observe.  Pinch  the  rubber 
tubing  together  to  extinguish  the  flame,  and  then,  hold- 
ing the  gauze  just  above  the  orifice,  light  the  gas  above 
the  gauze.  Raise  the  gauze  up  and  note  the  behavior 
of  the  flame.  If  the  gauze  were  made  of  a  material 
which  is  a  poor  conductor  of  heat,  how  do  you  think  it 
would  modify  the  phenomena  observed  ? 

EXPERIMENT  87.  Structure  of  Flame.  I.  A  candle 
flame.  Examine  a  candle  flame  in  a  place  free  from 
drafts,  observing  all  its  parts  with  their  colors,  and  make 
drawings  of  each  part.  Holding  it  before  a  blackboard 
or  other  dark  surface,  note  the  outer  portion.  Also  hold 
it  in  direct  sunlight  and  examine  the  shadow  it  casts  on 
white  paper.  Holding  a  piece  of  sized  paper  (asbestos 
paper  is  better)  horizontally  with  both  hands,  press  it 
down  for  a  moment  or  so  on  the  flame  nearly  to  the  wick, 
and  examine  the  charred  or  sooty  portions  of  the  paper. 

II.  A  Bunsen  flame.  Repeat  the  above  experiments 
with  a  Bunsen  flame  instead  of  a  candle  flame.  Hold  a 
match  stick  across  the  orifice  of  the  burner  and  note  how 


Experiments  67 

the  wood  is  charred.  Hold  it  just  above  the  inner  cone 
and  note  what  happens.  Draw  out  one  end  of  a  piece  of 
glass  tubing  to  a  bore  of  a  little  less  than  a  millimeter, 
thrust  the  wider  end  into  the  inner  cone  and  ignite  the 
gas  escaping  from  the  drawn-out  end.  Slowly  raise  the 
tube  until  its  wider  end  comes  above  the  inner  cone  and 
note  what  happens.  Thrust  a  pin  through  a  match  near 
its  head  and  put  the  stick  into  a  burner.  Turn  on  the 
gas  and  light  it  above  the  match.  Hold  a  piece  of  new 
asbestos  paper  or  board  vertically  so  as  to  divide  the 
flame  in  halves  and  note  how  it  is  charred. 

EXPERIMENT  88.  Luminosity  of  Flame.  Sprinkle 
a  little  charcoal  dust  into  a  non-luminous  flame ;  also 
rub  two  pieces  of  charcoal  together  near  the  airholes 
of  a  Bunsen  burner  so  that  the  dust  may  be  carried  up 
into  the  flame  by  the  inflow  of  the  air.  What  is  the 
effect  upon  the  flame  ?  Stir  up  the  dust  in  the  vicinity 
of  a  non-luminous  flame.  Close  up  the  airholes  of  a 
Bunsen  burner,  and  essay  an  explanation  for  the  lumi- 
nosity of  the  flame  thus  produced.  Examine  a  Wels- 
bach  burner  and  mantle.  Wherein  does  the  Welsbach 
burner  resemble  the  Bunsen  burner  ?  What  is  the 
function  of  the  mantle? 

EXPERIMENT  89.  Speed  of  Propagation  of  Flame. 
Slowly  turn  off  the  gas  of  a  Bunsen  flame  so  as  to 
diminish  its  speed  of  outflow  very  gradually.  What 
happens  ?  This  is  because  the  speed  of  flow  of  the  gas 
becomes  less  than  that  of  the  flame.  Now  turn  the  gas 
full  on.  At  what  two  orifices  is  the  flame  now  burning  ? 
What  was  the  cause  of  the  slight  explosion  ? 

EXPERIMENT  90.  Oxidizing  and  Reducing  Flames. 
Cut  out  a  little  cavity  in  a  piece  of  charcoal,  pack  it 
nearly  full  of  litharge  (lead  oxid),  and  direct  the  reduc- 
ing flame  of  a  blowpipe  steadily  upon  it  for  some  time. 
Examine  the  lead  obtained.  Now  place  a  bit  of  lead 

6 


68  Elementary  Chemistry 

in  a  cavity  in  a  piece  of  charcoal  and  direct  the  oxidiz- 
ing flame  upon  it.  Note  the  fumes  and  the  color  of 
the  coating  on  the  charcoal. 

SALTS,  ACIDS,  AND   BASES 

EXPERIMENT   91.    General   Properties   of   Acids. 

Fill  a  beaker  with  distilled  water,  and  after  rinsing  off 
a  glass  rod,  dip  it  into  the  distilled  water  and  place  the 
drop  that  adheres  to  it  on  the  tongue,  noting  its  taste. 
Rinse  the  rod  again — it  must  be  washed  after  each  test 
—and  by  means  of  it  place  a  drop  of  the  distilled  water 
on  a  piece  of  blue  and  of  pink  litmus  paper,  being  sure 
that  the  paper  is  on  a  clean  surface.  What  change  of 
color  ? 

Pour  about  ioc-c-  of  the  distilled  water  into  a  clean 
test  tube,  add  not  more  than  three  drops  of  strong  sul- 
furic  acid,  and  stir  well  together.  In  the  same  manner 
as  before  taste  this  acid  solution  and  ascertain  its  action 
on  pink  and  on  blue  litmus  paper. 

Perform  similar  tests  with  very  dilute  solutions  of 
any  other  acids  which  are  available,  as  nitric,  acetic, 
hydrochloric,  tartaric. 

Review  Experiment  18  and  state  what  is  the  general 
action  of  dilute  acids  on  metals.  Test  the  action  of  acids 
on  any  other  indicators  which  may  be  available,  such  as 
Congo  red,  phenolphthalein,  methyl  orange. 

EXPERIMENT  92.  General  Properties  of  Bases. 
Dissolve  a  piece  (3  mm-)  of  sodium  hydroxid  in  about 
IQC.C.  of  water  in  a  test  tube.  Pour  a  drop  or  so  on 
your  finger  and  rub  it  with  another  finger.  What  is 
the  feel?  Dilute  a  little  of  this  solution  with  about 
twenty  times  its  volume  of  water,  and,  using  a  stirring 
rod,  cautiously  taste  a  drop.  If  the  taste  is  not  decided 
enough,  add  a  little  more  of  the  sodium  hydroxid  solu- 
tion. Find  what  effect  the  solution  has  on  pink  and  on 


Experiments  69 

blue  litmus  paper  as  well  as  upon  any  other  indicators 
available.  Repeat  these  tests  with  potassium  hydroxid 
instead  of  sodium  hydrcxid ;  also  ammonium  hydroxid 
(review  Experiment  54),  and  with  lime  water  (calcium 
hydroxid,  Ca(OH)2,  solution). 

EXPERIMENT  93.  Neutralization.  Place  about  5^- 
of  a  very  weak  solution  of  sodium  hydroxid  in  an  evap- 
orating dish,  and  add  a  little  litmus  solution  or  any 
other  indicator.  Then  with  constant  stirring  add  (a 
drop  or  so  at  a  time)  dilute  hydrochloric  acid  until  the 
blue  color  changes  into  a  lavender.  If  too  much  acid  is 
added,  the  color  will  be  pink.  In  that  case  add  some 
more  sodium  hydroxid  solution,  a  drop  at  a  time,  so  as 
to  get  the  color  just  blue,  and  then  a  very  small  drop 
of  the  acid.  When  the  intermediate  color  has  been 
obtained,  evaporate  to  dryness.  Examine  the  product 
as  to  its  physical  properties  and  try  its  action  on  litmus 
paper,  as  well  as  upon  other  indicators  that  you  may  hap- 
pen to  have  at  hand.  What  is  the  substance  ?  Repeat 
these  operations,  using  dilute  nitric  acid  instead  of 
hydrochloric. 

OXIDS  OF  NITROGEN;    NITRIC  ACID 

EXPERIMENT  94.  Preparation  and  Properties  of 
Nitrous  Oxid.  Put  about  15^-  (6cm-  circle)  of  ammo- 
nium nitrate,  NH4NO3,  into  a  flask  (or  retort)  provided 
with  a  delivery  tube  and  an  interposed  safety  bottle28 
(Fig.  51).  Heat  the  flask  gently  and  collect  a  couple 
of  receivers  full  of  the  gas  by  water  displacement. 
Plunge  a  lighted  splinter  of  wood  into  a  receiver  full 
of  the  gas.  Is  the  gas  combustible  or  a  supporter  of 
combustion  ?  Set  a  little  red  phosphorus  or  sulfur  on 
fire  in  a  combustion  spoon  and  introduce  it  into  the  gas. 
What  other  gas  behaves  in  a  fashion  similar  to  nitrous 
oxid  ?  How  would  you  distinguish  the  two  gases  ? 


Elementary  Chemistry 


Fig.   51  APPARATUS    FOR    PREPARING    NITROUS    OXID 

EXPERIMENT  95.  Nitric  Oxid ;  Its  Preparation 
and  Properties.  Put  about  io&  of  copper29  (in  the 
form  of  filings,  turnings,  bits  of  wire,  or  granulated)  in 
a  gas  generator;  just  cover  it  with  water30  and  add 
enough  strong  nitric  acid  to  cause  a  brisk  evolution  of 
the  gas.  Add  water  if  the  reaction  becomes  too  tumul- 
tuous. Collect  by  water  displacement  six  receivers  full 
of  the  pure  gas,  saving  two  receivers  full  for  Experi- 
ment 98.  Let  a  little  of  the  gas  escape  from  one  of  the 
receivers.  What  causes  it  to  turn  brown  as  soon  as  it 
comes  in  contact  with  the  air  ?  Insert  a  lighted  splin- 
ter into  one  of  the  receivers.  Is  the  gas  combustible 
or  a  supporter  of  combustion  ?  Introduce  a  combustion 
spoon  containing  burning  red  phosphorus  into  a  receiver 
full.  Compare  the  result  with  that  obtained  with 
nitrous  oxid. 

NOTE  29.  Ferrous  Sulfate.  Ferrous  sulfate  (also  known  as 
green  vitriol  and  copperas)  may  be  advantageously  substituted  for 


Experiments  ji 

the  copper.  It  should  be  in  the  form  of  small  lumps  or  crystals, 
and  strong  nitric  acid  added.  The  reaction  is  more  easily  con- 
trolled and  a  purer  gas  is  obtained. 

NOTE  30.  Use  Hot  Water.  As  nitrous  oxid  is  rather  soluble 
in  cold  water,  it  is  advisable  to  have  the  pneumatic  trough  filled 
with  as  hot  water  as  convenient. 

EXPERIMENT  96.  Volumetric  Composition  of 
Nitric  Oxid.  Obtain  a  glass  tube  about  20  cm-  long 
and  of  about  i cm-  bore,  sealed  at  one  end.  Fit  over  the 
open  end  a  piece  of  tightly-fitting  rubber  tubing  about 
gem.  long  and  have  ready  two  Hofmann  clamps  (Fig. 
52).  Fill  the  glass  and  rubber  tube  with  water  and 
then  displace  the  water  with  pure  nitric  oxid,  prepared 
by  the  reduction  of  nitric  acid  by  ferrous  sulfate.  Pinch 
the  tube  tightly  near  the  glass  tube  with  one  of  the 
clamps,  A,  and,  removing  the  tube  from  the  water,  fill 
the  rubber  tube  nearly  full  with  an  intimate  mixture  of 
equal  bulks  of  powdered  iron  and  sulfur.  Then  close 
the  tube  near  its  end  with  the  second  clamp,  B.  Now 
open  the  first  clamp  so  that  the  mixture  of  iron  and 
sulfur  may  fall  into  the  tube.  Shake  the  tube  at  inter- 
vals of  fifteen  to  twenty  minutes.  Then  turn  the  tube 
upside  down  and  shake  as  much  as  possible  of  the  solid 


Fig.   52 APPARATUS    FOR    DETERMINING    THE    VOLUMETRIC    COMPOSITION 

OF    NITRIC    OXID 

mixture  clown  into  the  rubber  tubing.  Close  the  clamp 
A,  as  before,  open  clamp  />,  and  after  shaking  out  the 
solid  mixture,  fill  the  rubber  tubing  brimful  of  water, 
close  it  with  the  thumb  and  place  the  tubing  under 
water.  Now  open  clamp  A  What  happens? 

With  a  rubber  band  or  piece  of  cotton  cord  mark  the 
volume  of  the  gas  remaining.  What  gas  is  it  ?  Ascer- 
tain the  volume  of  this  and  that  of  the  nitric  oxid  taken 


72  Elementary  Chemistry 

at  first  by  running1  in  water  from  a  burette  or  by  weigh- 
ing-. What  conclusion  do  you  draw  as  to  the  volume  of 
oxygen  and  nitrogen  composing  nitric  oxid  ? 

*  EXPERIMENT  97.  Nitrogen  Dioxid.  Heat  in  a  test 
tube  a  few  crystals  of  manganous  nitrate,  Mn(NO3)2, 
or  lead  nitrate,  Pb(NO3)2.  The  main  gaseous  product 
is  nitrogen  peroxid.  Is  it  soluble  in  water  ? 

EXPERIMENT  98.  Illustration  of  the  Law  of  Vol- 
umetric Proportions*  Prepare  two  gasometric  tubes 
as  follows  :  Obtain  two  test  tubes  about  2$cm-  long  and 
i  cm-  wide.  Fill  the  small  tube  even  full  of  water  and 
empty  it  into  one  of  the  large  tubes,  and  mark  the 
position  of  the  water  level  with  a  rubber  band.  Add  a 
second  tube  full  and  mark  the  position  of  the  water 
level,  and  continue  in  this  way  until  the  tube  is  full. 
Proceed  in  like  manner  with  the  second  large  tube. 

Introduce  into  one  of  the  gasometric  tubes  two  vol- 
umes of  nitric  oxid  (best  prepared  from  nitric  acid  and 
ferrous  sulfate),  and  into  the  other,  five  volumes  of  air. 
Pass  the  contents  of  one  tube  into  the  other.31  What 
is  observed  ?  In  two  or  three  minutes  read  the  volume 
of  the  residual  gas.  What  gas  is  formed  when  nitric 
oxid  comes  in  contact  with  oxygen  ?  Is  it  soluble  in 
water  ?  Explain  the  contraction. 

Repeat  this  procedure  at  least  twice,  so  as  to  be  sure 
of  the  results,  each  time  transferring  the  residual  gas 
into  a  receiver  so  that  it  may  be  examined  and  tested  as 
follows  :  Measure  out  from  the  receiver  three  volumes 
and  add  a  measured  volume  of  air.  Is  there  any  con- 
traction ?  If  so,  add  some  more  air,  and  see  if  there  is 
any  contraction.  In  the  same  fashion,  add  volumes  of 
nitric  oxid  to  a  measured  volume  of  the  residual  gas 
and  continue  the  additions  until  there  is  no  contraction. 
Point  out  in  detail  how  this  experiment  illustrates  the 
law  in  question. 


Experiments 


73 


NOTE  31.  Transferring  Gases.  To  transfer  gases  from  ©ne 
vessel  into  another,  the  pneumatic  trough  must  be  deep  enough 
to  allow  of  the  complete  submerging  of  the  vessels.  They  are 
then  placed  so  that  the  gas  from  one  may  rise  and  displace  the 
water  in  the  other. 

EXPERIMENT  99.  Preparation  and  Properties  of 
Nitric  Acid.  Put  into  a  retort  about  15  ff.  (5  cm-  circle) 
of  powdered  soditim  or  potassium  nitrate  and  add  about 
30  c.c.  of  strong  sul- 
furic  acid.  Arrange 
the  apparatus  (Fig. 
53)  so  that  the  retort's 
neck  passes  nearly  to 
the  bottom  of  a  test 
tube  or  flask  set  in  a 
dish  filled  with  cold 
water.  Heat  gently 
with  interposed  wire 
gauze,  noting  the  be- 
havior of  the  mixture 
in  the  retort.  When 
the  test  tube  is  about  a  quarter  full  of  the  distillate 
remove  the  flame  ;  be  sure  that  the  end  of  the  retort's 
neck  is  not  dipping  below  the  surface  of  the  acid  in  the 
test  tube. 

CAUTION.  Be  very  careful  not  to  spill  nitric 
acid  on  the  hands;  it  produces  very  bad  burns. 

Note  the  color  of  the  nitric  acid  thus  prepared,  and 
compare  it  with  that  of  a  freshly-opened  bottle  of  the 
commercial  "c.  p."  article.  How  do  you  account  for 
the  difference  ?  Cautiously  note  its  odor.  Pour  a  few 
drops  on  a  glass  plate  or  watch  crystal  and  place  beside 
it  a  glass  plate  or  watch  crystal  containing  a  little 
strong  ammonia  water.  How  do  you  account  for  the 
result  ?  Put  a  bit  of  litmus  paper  in  a  dish  and  add  a 
few  drops  of  acid  from  the  test  tube ;  repeat  after 


Fig.    S3 PREPARING    NITRIC    ACID 


74  Elementary  Chemistry 

diluting  the  acid  with  about  four  times  its  volume  of 
water.  Take  up  a  drop  on  a  stirring"  rod  and  touch  it 
to  your  finger-nail  or  a  quill ;  wash  it  off  promptly  and 
put  on  a  drop  of  ammonium  hydroxid.  Test  its  action 
both  when  cold  and  when  hot  on  a  little  of  the  follow- 
ing metals  placed  in  separate  test  tubes  :  iron,  copper, 
zinc,  lead,  and  mercury.  Pour  a  drop  or  so  into  a  little 
indigo  solution.  Put  a  drop  on  a  piece  of  newspaper 
and  on  a  piece  of  the  best  linen  writing  paper.  Is  the 
difference  in  the  action  sufficient  to  distinguish  news- 
paper (which  is  made  from  wood  pulp)  from  writing 
paper  (which  is  made  from  Jinen  rags)?  What  is  the 
paper  of  your  notebook  made  of,  wood  pulp  or  linen? 

EXPERIMENT  100.  Decomposition  of  Nitric  Acid 
by  Heat.  Support  a  long-stemmed  tobacco  pipe  on  a 
stand  so  that  its  mouthpiece  just  dips  below  the  water 
in  a  dish,  Heat  the  stem  red-hot  with  a  Bunsen  flame 
and  then  pour  a  few  drops  of  concentrated  nitric  acid 
into  the  bowl  so  that  it  may  flow  down  through  the 
heated  portion.  What  makes  the  bubbles  have  a 
reddish-brown  color  while  the  gas  which  collects  in 
the  receiver  is  colorless  ?  Into  what  three  substances 
is  the  nitric  acid  decomposed  ? 

EXPERIMENT  101.  Reduction  of  Nitric  Acid  to 
Ammonia.  Put  a  little  granulated  zinc  into  a  test  tube 
and  add  about  5  c-c-  of  dilute  sulfuric  acid.  After  the 
hydrogen  is  escaping  freely,  add  a  drop  at  a  time  (a 
"medicine  dropper"  will  be  found  convenient,  or  a  little 
pipette  easily  made  by  drawing  out  to  a  jet  a  piece  of 
glass  tubing),  very  dilute  nitric  acid,  noting  carefully 
what  happens  when  each  drop  is  added.  Add  only 
about  a  dozen  drops  of  the  nitric  acid.  After  a  few 
minutes  pour  part  of  the  solution  into  another  test 
tube  and  add  an  excess  of  caustic  soda  solution.  Warm 
a  little  and  cautiously  smell  of  the  contents  of  the  tube. 


Experimcn  ts  75 

What  evidence  is  there  that  ammonia  is  being  given 
off  ?  Verify  your  conclusion  by  the  use  of  litmus  paper 
and  by  Nessler's  solution.  How  do  you  explain  the 
formation  of  the  ammonia  ? 

EXPERIMENT  102.  Reduction  of  a  Nitrate  to  a 
Nitrite.  Heat  15^-  of  sodium  or  potassium  nitrate  with 
30^-  of  lead  in  an  iron  dish  (sand  bath  pan),  stirring  the 
melted  mixture  with  a  stiff  iron  wire  or  long  nail  until 
most  of  the  lead  has  disappeared.  Transfer  the  cooled 
mass  to  a  mortar,  grind  it  to  a  powder,  add  hot  water, 
stir  well  and  filter.  To  a  portion  of  the  filtrate  add  a 
few  drops  of  concentrated  sulf uric  acid,  or  potassium  or 
barium  nitrate.  The  yellowish-brown  powder  formed 
during  the  heating  is  lead  oxid.  What  is  the  source  of 
the  oxygen  combining  with  the  lead  ?  How  must  the 
nitrate  have  been  changed  ? 

PREPARATION  AND  PROPERTIES  OF  ACIDS, 
BASES,  AND  SALTS 

EXPERIMENT  103.  Preparation  of  a  Salt  (Mercury 
lodid)  by  Direct  Union  of  the  Elements.  Weigh  on 
a  watch  glass  2.5^-  of  mercury32,  and  then  also  on  a 
watch  glass  ^.2^-  of  iodin33.  Place  the  mercury  in  a 
clean  mortar  and  just  cover  it  with  alcohol34.  Add 
about  a  quarter  of  the  iodin  and  rub  it  gently  into  the 
mercury  until  the  iodin  as  such  seems  to  have  dis- 
appeared. Then  mix  in  a  second  quarter-portion  and 
continue  until  all  the  iodin  is  added  and  the  mixture  is 
dry  and  of  a  bright  red  color.  Transfer  the  product  to 
a  test  tube  and  add  about  5  c-c-  of  alcohol.  Heat  the 
alcohol  to  boiling  for  a  minute  or  so  by  immersing  the 
end  of  the  tube  in  boiling  water  contained  in  a  beaker. 
Pour  the  solution  into  an  evaporating  dish  and  set 
aside  to  cool.  Examine  carefully  the  crystals  of  mer- 
cury iodid  which  separate  out.  Place  a  few  of  them 


76  Elementary  Chemistry 

in  a  dry  test  tube  and  cause  them  to  sublime  by  heat- 
ing the  rounded  end  of  the  tube.  How  do  you  account 
for  the  different  colors  of  the  sublimate  ?  Rub  it  with 
a  glass  rod  and  note  any  change  of  color35. 

NOTE  32.  Pipette  for  Handling  Mercury.  A  convenient  way 
to  handle  small  quantities  of  mercury  is  by  means  of  a  little  pipette 
made  by  drawing  out  a  piece  of  narrow  glass  tubing  to  a  long, 
tapering  point.  Mercury  is  drawn  up  into  the  pipette  by  suction. 
If  the  tube  then  be  held  in  an  almost  horizontal  position,  the 
mercury  will  not  run  out,  and  may  be  nicely  discharged  where 
wan  ted"  by  inclining  the  pipette  a  little. 

NOTE  33.  Danger  of  Corrosion.  As  both  mercury  and  iodin 
corrode  brass,  great  care  must  be  exercised  not  to  let  them  or  their 
fumes  come  in  contact  with  the  brass  parts  of  a  balance.  Be  sure 
to  collect  any  of  either  element  whteh  may  become  scattered  about 
the  balance  through  careless  handling. 

NOTE  34.  Addition  of  Alcohol.  The  reason  for  adding  alcohol 
is  to  keep  down  the  temperature  (the  heat  of  the  reaction  will  be 
expended  largely  in  evaporating  the  alcohol)  and  to  bring  the 
iodin  and  mercury  in  more  intimate  contact.  The  alcohol  does 
not  participate  in  the  reaction  at  all. 

NOTE  35.  Iodin  Stains.  Iodin  stains  may  be  removed  by 
means  of  sodium  sulfite  or  ammonium  sulfid  solution. 

EXPERIMENT  104.  Preparation  of  a  Salt  (Zinc  Sul- 
fate)  by  the  Solution  of  a  Metal  (Zinc)  in  an  Acid 
(Sulfuric).  Place  about  5^-  of  zinc  in  a  beaker  or  flask 
and  add  about  40  c-c-  of  dilute  sulfuric  acid.  When  the 
evolution  of  hydrogen  has  nearly  ceased,  filter  the  solu- 
tion into  an  evaporating  dish  and  gently  heat 3  6  over  a 
wire  gauze  nearly  to  boiling,  until  a  thin  film  appears 
on  the  surface  of  the  solution.  Then  set  it  aside  so 
that  it  may  cool  slowly.  At  frequent  intervals  for 
several  days  examine  the  crystals  which  separate  out 
and  carefully  note  their  form.  Remove  them  from  the 
solution  and  dry  them  by  pressing  between  folds  of 
filter  paper.  Do  the  crystals  contain  water  of  crystal- 
lization ? 

NOTE  36.  Slow  Evaporation.  Instead  of  evaporating  off  the 
water  rapidly  by  heating,  the  dish  may  be  set  aside  so  that  the 
water  may  slowly  evaporate  during  several  days.  If  this  be 
done,  better  and  larger  crystals  will  be  obtained. 


Experiments 


77 


EXPERIMENT  105.  Preparation  of  a  Salt  (Ammo- 
nium C/tlorid)  by  the  Neutralization  of  Ammonium 
Hydroxid  by  Hydrochloric  Acid.  Dilute  25  c-c.  of  con- 
centrated hydrochloric 
acid  with  an  equal  vol- 
ume of  water,  mix  well, 
and  fill  a  burette  with  the 
mixture  3  7.  Fill  a  second 
burette  with  concentrated 
ammonium  hydroxid 
(Fig.  54).  Run  5.0^-  of 
the  acid  into  an  evaporat- 
ing dish  which  has  pre- 
viously been  weighed  to 
centigrams,  and  add  just 
enough  litmus  solution  to 
impart  a  distinctly  pink 
color.  Note  the  reading 
on  the  burette  containing 
the  ammonium  hydroxid, 
and  run  the  solution,  a 
few  drops  at  a  time,  into 
the  acid,  with  constant 
stirring,  until  the  red 
color  turns  to  blue.  Then 
run  in  the  acid,  drop  by 
drop,  stirring  after  each 
addition,  until  the  color  is 
half-way  between  blue  and 
red.  Evaporate  the  solu- 
tion to  dryness  on  a  water 
bath  2  2  (the  ammonium  chlorid  volatilizes  at  a  higher  tem- 
perature), let  cool  and  weigh.  Again  heat  for  a  quarter  of 
an  hour  and  weigh,  continuing  in  this  way  until  the  salt 
is  perfectly  dry,  as  shown  by  no  further  loss  in  weight. 


Fig.  54 — BURETTES  ARRANGED    FOR  NEU- 
TRALIZING   A    BASE    BY    AN   ACID    TO    PRO- 
DUCE   A    SALT 


78  Elementary  Chemistry 

The  equation  for  this  neutralization  reaction  may  be 
written  thus  : 

NH4OH  +  HC1  ->  NH4C1  +  H2O 

How  many  grams  of  NH4C1  have  you  prepared  ?  Calcu- 
late how  much  NH4OH  and  HC1  were  needed.  How 
much  NH4OH  and  HC1  were  contained  in  the  volume 
of  the  solutions  used?  Calculate  how  many  grams  of 
NH4OH  and  of  HC1  there  would  be  in  a  liter  of  a  solu- 
tion of  the  same  concentration. 

NOTE  37.  Drying  the  Burette.  If  the  burette  is  not  perfectly 
dry,  it  should  be  rinsed  out,  delivery  tube  and  all,  with  a  few 
cubic  centimeters  of  the  acid  before  filling.  The  ammonium 
hydroxid  burette  should  also  be  rinsed  out  with  that  liquid. 

EXPERIMENT  106.  The  Solubility  Product.  Pre- 
pare a  saturated  solution  of  sodium  chloric!,  NaCl,  by 
shaking  the  solid  in  a  test  tube  with  water  until  no 
more  is  dissolved.  The  solution  will  not  be  accelerated 
by  heating,  as  sodium  chlorid  is  nearly  as  soluble  in 
cold  water  as  in  hot.  Fill  a  test  tube  a  quarter  full 
with  this  saturated  solution.  Put  a  few  cubic  centi- 
meters of  concentrated  hydrochloric  acid  in  a  test  tube 
provided  with  a  cork  and  delivery  tube,  heat  gently, 
and  pass  the  hydrogen  chlorid  expelled  from  solution 
into  the  solution  of  salt.  Prove  experimentally  that 
the  white  substance  precipitated  is  sodium  chlorid,  and 
explain  its  formation. 

THE  HALOGENS  AND  THEIR  HYDROGEN 
COMPOUNDS 

EXPERIMENT  107.  Chlorin  by  Oxidization  of  Hy- 
drochloric Acid.  Into  separate  test  tubes  put  a  pinch 
of  potassium  chlorate,  of  red  lead,  and  of  potassium 
dichromate,  and  add  a  little  strong  hydrochloric  acid  to 
each.  If  a  reaction  does  not  take  place  promptly,  warm 
a  little.  Note  the  physical  properties  of  the  gaseous 


Experiments 


79 


product,  and  then  stop  the  action  by  filling  the  tube  up 
with  water.  What  are  the  color  and  other  properties 
of  this  solution  ? 

EXPERIMENT  108.  Preparation  of  Chlorin.  I. 
(Hood.)  Into  a  flask  (200  to  300  c-c-}  fitted  with  a  delivery 
tube  and  an  interposed  safety  bottle  (Fig.  55),  put  about 
20  ff-  (5^- circle)  of 
manganese  dioxid 
and  add  to  it  50^- 
strong  hydro- 
chloric acid.  The 
delivery  tube 
should  reach  to 
the  bottom  of  the 
receiver,  which 
should  be  snugly 
covered  with  a 
piece  of  cardboard 
pierced  with  a 
hole  for  the  pas- 
sage of  the  delivery  tube.  Heat  the  flask  gently  and 
collect  by  downward  displacement  four  receivers  full 
of  the  gas.  You  can  tell  by  the  greenish  color  when 
the  receivers  are  full,  and  the  full  receivers  should  be 
covered  with  glass  slips  smeared  with  a  little  vaseline 
so  as  to  make  gas-tight  joints.  Pass  to  Experiment  no. 

EXPERIMENT  109.  Preparation  of  Chlorin.  II. 
(Hood.)  Into  a  gas  generator  fitted  with  a  stopcock 
funnel  (Fig.  18)  put  about  enough  of  bleaching  powder 
to  cover  the  bottom  of  the  generator  to  a  depth  of  a 
centimeter.  The  delivery  tube  should  reach  to  the  bot- 
tom of  the  receiver,  which  should  be  covered  with  a 
piece  of  cardboard  with  a  hole  through  it  for  the  passage 
of  the  delivery  tube.  Let  strong  hydrochloric  acid  drop 
from  the  funnel  upon  the  bleaching  powder  just  fast 


Fig.   55 PREPARING  CHLORIN 


8o  Elementary  Chemistry 

enough  to  keep  up  a  brisk  evolution  of  the  gas,  and  col- 
lect four  receivers  full  by  downward  displacement,  cov- 
ering a  receiver  when  full  (as  shown  by  the  green  color) 
with  a  glass  slip  smeared  with  vaseline.  Pass  to  Ex- 
periment no. 

EXPERIMENT  no.  Properties  of  Chlorin.  (Hood.) 
Thrust  a  piece  of  flaming  paper  into  a  receiver  filled 
with  chlorin,  moving  the  glass  slip  only  a  little  aside 
and  at  once  covering  the  receiver  again  so  as  to  prevent 
the  fumes  from  escaping.  Is  the  gas  combustible? 
Does  it  support  combustion  ?  Moving  the  glass  slip 
aside  again,  sprinkle  a  pinch  of  powdered  antimony 
into  the  gas.  Also  introduce  a  loose  bundle  of  very 
fine  brass  or  copper  wires  which  have  been  heated  to 
redness.  Is  the  gas  a  supporter  of  combustion  ?  Com- 
pare it  in  this  respect  with  oxygen. 

Into  a  second  receiver  put  some  paper  with  writing 
(both  by  ink  and  by  pencil)  on  it  and  some  pieces  of 
dry  calico,  and  into  a  third  some  paper  with  writing  on 
it  and  some  pieces  of  moistened  calico.  What  differ- 
ences are  to  be  observed  in  the  bleaching  action  in  the 
two  receivers  ?  Repeat  with  the  fourth  receiver  any  of 
the  above  experiments,  the  results  of  which  you  are  in 
doubt  about  and  wish  to  verify. 

EXPERIMENT  m.  Chlorin  Water.  Drop  into  a 
test  tube  a  few  small  crystals  of  potassium  chlorate, 
cover  them  with  concentrated  hydrochloric  acid  diluted 
with  an  equal  volume  of  water,  warm  a  little,  and  as 
soon  as  the  chlorin  begins  to  escape  from  the  tube,  fill 
it  nearly  full  of  water.  Pour  a  little  indigo  solution 
into  a  test  tube  and  add  an  equal  volume  of  the  chlorin 
water.  Is  the  color  discharged  ?  Try  the  action  of  the 
chiorin  water  on  solutions  of  litmus,  of  cochineal,  and 
of  copper  sulfate.  Explain  any  differences  in  the 
bleaching  action. 


Experiments 


81 


EXPERIMENT  112.  Preparation  and  Properties  of 
Bromin.  Put  about  10^-  (^cm-  circle)  of  potassium 
bromid  in  a  mortar  and  add  an  equal  bulk  of  man- 
ganese dioxid.  Mix  them  well  together  and  introduce 
the  mixture  into  a  dry  retort,  and  then  add  about  ioc-c- 
of  concentrated 
sulfur ic  acid. 
Support  the  re- 
tort on  the  stand 
so  that  its  neck 
may  enter  a  test 
tube  or  flask  set 
in  a  dish  filled 
with  cold  water 
(Fig.  56).  Put  a 
little  water  in  the 
test  tube  and  ad- 
just  so  that  the 

neck  of  the  retort  just  dips  into  the  water.  Heat  the 
retort  very  gently  and  collect  the  bromin  given  off  until 
no  more  red  vapor  is  seen  in  the  retort.  Note  the  phys- 
ical properties  of  the  bromin. 

Pour  a  drop  or  so  of  bromin  into  a  dry  receiver, 
cover  with  a  piece  of  paper  or  a  glass  slip,  and  shake 
and  invert  the  receiver  so  that  the  bromin  may  rapidly 
vaporize  and  its  vapors  fill  the  vessel.  Try  its  bleach- 
ing action  as  was  done  with  chlorin  and  compare 
results.  Pour  what  bromin  is  left  into  the  bottle 
labeled  "Bromin"  which  is  standing  on  the  side  table. 

EXPERIMENT  113.  Preparation  and  Properties  of 
lodin.  Grind  well  together  in  a  mortar  a  half  dozen 
crystals  of  potassium  iodid  with  an  equal  bulk  of  man- 
ganese dioxid,  put  the  mixture  in  an  Erlenmeyer  flask, 
and  add  about  15^-  of  a  mixture  of  equal  volumes  of 
concentrated  sulfuric  acid  and  water.  (Pour  the  acid 


82 


Elementary  Chemistry 


into  the  water,  not  the  water  into  the  acid.)  Set  the 
flask  on  a  wire  gauze  on  a  ring  stand,  and  insert  in 
its  neck  loosely  a  perforated  cork  holding  a  small  test 
tube  filled  with  cold  water  (Fig.  57).  Another  appara- 
tus is  a  tall,  slender  beaker  with  a  watch  glass  cover- 
ing it  and  filled  with  cold 
water  (Fig.  58).  Heat  the 
flask  with  a  very  small 
flame,  just  enough  to 
cause  the  iodin  liberated 
from  the  potassium  iodid 
to  vaporize  and  collect  on 
the  sides  of  the  test  tube 
kept  at  a  low  temperature 
by  the  cold  water.  When 
the  test  tube  is  covered 
with  crystals  of  iodin,  dis- 
continue the  heating,  re- 
move the  test  tube,  and 
scrape  the  iodin  into  an 
evaporating  dish.  Note 
its  physical  properties. 

Fig.   57 PREPARING    IODIN  '       ln  J      1    . 

Heat  a  small  crystal  in 

a  dry  test  tube  and  when  the  tube  is  filled  with  the 
vapor,  invert  it  and  draw  conclusions  as  to  the  relative 
weights  of  air  and  iodin  vapor.  Touch  your  finger  to 
a  crystal.  What  is  the  color  of  the  stain  ?  Will  water 
remove  it  ?  Will  alcohol  ?  Will  a  solution  of  potassium 
iodid?  In  which  of  these  three  liquids  is  iodin  readily 
soluble?  Place  the  rest  of  the  iodin  in  the  bottle 
labeled  "  Iodin  "  which  is  standing  on  the  side  table. 

EXPERIMENT  114.  Tests  for  Free  Bromin  and 
Iodin.  Prepare  a  test  tube  full  of  chlorin  water  (Ex- 
periment in).  Dissolve  a  bit  of  potassium  iodid  and  of 
potassium  bromid  not  larger  than  a  pinhead  in  a  small 


Experiments 


test  tube  a  quarter  full  of  water,  a  different  test  tube 
for  each  substance.  Make  some  thin  starch  paste  by 
rubbing  up  a  small  lump  (5  mm-)  of  starch  with  a  little 
water  in  a  mortar  to  the  consistence  of  cream,  and  then 
boiling  it  in  an  evaporating  dish  with  about  50^-  of 
water  until  it  is  clear. 
Pour  three  or  four 
drops  of  this  starch 
paste  into  10^-  of 
water  in  a  test  tube 
and  shake  it  up  well ; 
then  add  a  drop  of  an 
aqueous  solution  of 
iodin.  What  is  the 
change  in  color? 
Heat  the  solution 
gently  until  the  color 
disappears,  and  then 
cool  it  by  immersing 
in  cold  water.  This 
is  a  very  delicate  test 
for  iodin  when  not  in 

Combination.     Repeat      Fig.  58  — ANOTHER  APPARATUS  FOR  PREPAR- 

this   test,   using   bro- 

min  water  instead  of  an  iodin  solution.     Is  the  test  as 

decisive  as  for  iodin  ? 

Pour  three  or  four  drops  of  starch  paste  into  10^- 
of  water  in  a  test  tube,  shake  it  up  well,  and  add  a  drop 
or  so  of  the  solution  of  potassium  iodid  you  have  pre- 
pared. Is  there  any  change  of  color  ?  Now  add  a  dozen 
or  so  drops  of  the  chlorin  water.  Explain  what  occurs. 
Repeat  with  the  solution  of  potassium  bromid  instead 
of  the  iodid.  Compare  the  results. 

Put  a  couple  of  drops  of  an  aqueous  solution  of 
iodin  in  about  ioc-c-  of  water  in  a  test  tube,  add  about 


84  Elementary  Chemistry 

2  c-c.  of  carbon  bisulfid,  and  shake  the  two  liquids  well 
together.  Does  the  color  of  the  carbon  bisulfid  change  ? 
Repeat,  using  a  solution  of  bromin  instead  of  iodin. 
Compare  the  two  results.  Repeat,  using  a  solution  of 
chlorin  water.  Does  this  give  a  decisive  test  ? 

Add  about  2  c-c-  of  carbon  bisulfid  to  the  solution  of 
potassium  iodid  prepared  and  shake  them  well  together. 
Does  the  color  change?  Add  a  few  drops  of  chlorin 
water  and  shake.  What  result?  Repeat,  using  the 
solution  of  potassium  bromid.  Compare  results.  Could 
you  prove  by  these  tests  that  bromin  was  present  in  a 
solution  of  unknown  composition  if  iodin  was  also  pres- 
ent? Try  it  on  a  mixture  of  potassium  bromid  and 
potassium  iodid  solutions. 

EXPERIMENT  115.  Action  of  Concentrated  Sulfuric 
Acid  on  Halid  Salts.  Place  in  separate  test  tubes  a 
couple  of  small  crystals  of  sodium  chlorid,  of  potassium 
bromid,  and  of  potassium  iodid,  and  add  to  each  about 
2  c-c-  of  concentrated  sulfuric  acid.  Cautiously  compare 
the  smells  of  the  gases  evolved.  Heat  gently  and  note 
the  appearance  of  any  colored  gases,  if  they  have  not 
been  noticeable  without  heating.  What  elements  are 
set  free  ? 

Put  a  pinch  of  calcium  fluorid  (fluorspar)  in  a  small 
test  tube  and  add  about  2  c-c-  of  concentrated  sulfuric 
acid.  Heat  until  a  gas  is  given  off  vigorously.  Note 
the  physical  properties  of  this  gas  and  after  five  min- 
utes or  so  pour  out  the  reacting  mixture  into  a  plentiful 
supply  of  water.  Wash  out  the  test  tube  and  see  if  the 
glass  has  lost  its  transparency  in  spots,  and  if  so,  account 
for  it. 

To  clean  the  test  tubes  pour  their  contents  out  into 
a  large  amount  of  water.  Do  not  run  water  into  tJie 
tubes  upon  the  hot  sulfuric  acid,  as  there  is  danger  of  an 
explosion. 


Experiments 


EXPERIMENT  116.  Preparation  and  Properties  of 
Hydrochloric  Acid.  Put  ioc-c-  of  cold  water  in  a 
beaker  and  add  to  it  slowly  and  with  constant  stirring, 
SQC.C.  of  concentrated  sulfuric  acid.  Set  the  mixture 
aside  to  cool.  Put  about  30^-  (6  cm-  circle)  of  common 
salt  in  a  flask  provided  with  a  safety  bottle  and  delivery 
tube,  to  the  end 
of  which  may  be 
attached  a  small 
funnel  (Fig.  59) 
or  a  straight  piece 
of  large  glass  tub- 
ing. Add  the  cold 
acid  and  heat 
gently  with  the 
funnel  attached 
to  the  end  of  the 
delivery  tube,  un- 
til the  gas  given 
off  is  nearly  all 
absorbed  by  the 
water  in  which 
the  rim  of  the  funnel  just  dips.  Then  collect  by  down- 
ward displacement  four  dry  receivers  of  the  gas,  cov- 
ering them  with  glass  plates  when  full.  Let  the  gas 
pass  into  some  distilled  water  contained  in  a  dish,  using 
the  funnel  attachment,  and  save  the  solution  for  Expe- 
riment 1 1 8. 

Invert  a  receiver  full  of  the  gas  and,  holding  its 
mouth  under  water  in  a  pneumatic  trough,  open  it. 
How  do  you  account  for  what  happens  ?  What  other 
gas  studied  has  exhibited  a  similar  property  ?  Thrust 
a  blazing  splinter  of  wood  into  a  second  receiver.  Does 
the  gas  burn  or  support  combustion  ?  Hold  a  piece  of 
wet  filter  paper  over  the  mouth  of  another  receiver. 


Fig.   59 PREPARING  HYDROCHLORIC  ACID 


86  Elementary  Chemistry 

What  is  the  cause  of  the  phenomenon?  Drop  in  the 
last  receiver  a  piece  of  filter  paper  moistened  with 
strong"  ammonia  water.  What  happens  ?  What  is  the 
substance  formed  ? 

EXPERIMENT  117.  Analysis  of  Hydrogen  Chlorid. 
(a)  Place  a  bit  (3  »»«•)  of  sodium  in  a  bulb  tube  (Fig.  60), 
support  it  horizontally,  and  connect  it  on  one  side  with  a 

generator  from  which  a  brisk 
current  of  hydrogen  chlorid 
(generated  by  dropping  con- 
Fig.  60  —  sutB  TUBE  centrated  sulfuric  acid  into 
concentrated  hydrochloric  acid  contained  in  a  stopcock 
generator)  is  issuing,  and  on  'the  other  with  a  delivery 
tube.  As  soon  as  all  the  air  has  been  swept  from  the 
tube  (How  can  that  be  told?),  heat  the  sodium  cau- 
tiously until  it  takes  fire.  Now  collect  in  a  test  tube  a 
sample  of  the  gas  given  off  and  discharge  it  into  a  flame. 
What  is  the  gas  ? 

When  the  sodium  no  longer  burns,  disconnect  the 
generator  (letting  the  gas  pass  into  water  by  means  of 
a  funnel,  as  described  in  Experiment  116),  and,  after 
the  bulb  tube  has  cooled,  break  it  open  and  prove  by 
appropriate  tests  that  common  salt,  NaCl,  has  been 
formed.  In  the  burning  of  the  sodium,  what  substances 
were  the  combustible  and  the  supporter  of  combustion, 
respectively  ? 

(b)  Put  some  manganese  dioxid  into  an  evaporating 
dish  and  heat  as  hot  as  possible  for  about  ten  minutes 
so  as  to  remove  all  moisture  from  the  dioxid.  Arrange 
an  apparatus .  as  shown  in  Fig.  31.  Place  in  the  tube 
some  of  the  manganese  dioxid  and  connect  with  the  gas 
generator.  As  the  hydrogen  chlorid  passes  through 
the  tube,  heat  the  manganese  dioxid  gently  by  just 
brushing  a  flame  along  the  tube.  Collect  the  gas  given 
off  over  water  and  establish  its  identity  by  suitable  tests. 


Experiments  87 

How  do  you  account  for  the  moisture  that  collects  just 
beyond  the  dioxid  ? 

EXPERIMENT  118.  Tests  for  Chlorids,  Bromids, 
and  lodids.  Prepare  dilute  solutions  (about  3  per  cent) 
of  sodium  chlorid,  of  potassium  bromid,  and  of  potas- 
sium iodid.  To  a  few  drops  each  of  these  solutions  add 
an  equal  volume  of  silver  nitrate  solution.  Compare 
the  colors  and  properties  of  the  precipitates.  Boil  the 
solutions  and  note  the  behavior  of  the  precipitates.  Add 
ammonium  hydroxid  until  pieces  of  litmus  paper  placed 
in  the  tubes  are  blue,  shake  well,  and  note  which  pre- 
cipitates dissolve.  What  is  the  effect  of  adding  enough 
nitric  acid  to  make  the  litmus  red  ? 

Add  silver  nitrate  solution  to  a  little  of  the  solution 
of  hydrogen  chlorid  prepared  in  Experiment  116,  and 
to  as  many  chlorids,  bromids,  and  iodids  as  are  available. 
How  do  all  the  results  compare  ?  How  can  a  test  for  a 
fluorid  be  devised  from  Experiment  115  ? 

EXPERIMENT  119.  {Quantitative.}  To  Find  the 
Atomic  Weight  of  Chlorin.  Clean,  dry,  and  weigh 
to  centigrams  an  evaporating  dish.  Fill  it  about  one- 
fourth  full  of  finely  powdered  sodium  chlorid  and  heat 
until  decrepitation  ceases.  Let  cool  and  weigh.  Cover 
the  salt  with  strong  nitric  acid,  evaporate  to  dryness  on 
a  water  bath,  and  heat  with  free  flame  until  the  sodium 
nitrate  which  has  been  formed  just  begins  to  melt.  Let 
cool  and  weigh.  To  make  sure  that  all  the  chlorin  has 
been  expelled,  moisten  the  salt  with  concentrated  nitric 
acid,  heat  and  weigh  again,  repeating  until  a  constant 
weight  is  obtained. 

The  reaction  is  : 

NaCl  +  HN03  — >  NaNO3  +  HC1 

A  known  weight  (a)  of  sodium  chlorid  is  converted  into  a 
known  weight  (6)  of  sodium  nitrate.  If  the  atomic  weight  of 
chlorin  be  denoted  by  .r,  and  those  of  sodium,  nitrogen,  and 


88  Elementary  Chemistry 

oxygen  arc  23,  14,  and  16,  respectively,  then  the  molecular  weight 
of  NaCl  is:  +^ 

and  that  of  NaNO3  is  : 

23  +  14  + (3  X  16)1=85 

a     23  +  x 
Then    -=— 
b         8 

85  a  —  23  b 

and     x  =  — 

b 

EXPERIMENT  120.  (Quantitative^  To  Ascertain 
the  Strength  of  a  Given  Sample  of  Hydrochloric 
Acid.  Fill  a  burette  with  the  acid  to  be  tested.  Put 
about  IQC-C-  of  a  5  per  cent  solution  of  sodium  hydroxid 
in  an  evaporating  dish,  and  add  a  few  drops  of  some 
indicator.  Run  the  acid  into  the  alkali  with  constant 
stirring  until  neutralization  is  obtained.  Evaporate  to 
dryness  without  spattering.  Heat  the  dish  to  constant 
weight.  Calculate  the  weight  of  hydrogen  chlorid  in 
one  liter  of  the  solution. 

The  equation  for  the  neutralization  of  sodium  hydroxid  by 
hydrochloric  acid  is : 

NaOH  +  HC1— >  NaCl  +  H2O 

40  +  36.5  58-5  +  18 

from  which  it  is  seen  that  58. $&•  of  NaCl  are  formed  when  36. 5 £• 
of  HC1  are  used.  The  weight  of  the  HC1  in  the  volume  of  the 
solution  taken  stands  then  in  the  same  ratio  to  the  weight  of  the 
NaCl  found  as  does  36.5  to  58.5.  The  weight  of  HC1  contained 
in  a  liter  of  the  acid  solution  is  calculated  by  means  of  the  pro- 
portion : 

Volume  of  acid  taken  inc-c.         Weight  of  acid  found 
1,000  c-c-  x 

EXPERIMENT  121.  (Quantitative^]  To  Find  the 
Strength  of  a  Given  Sample  of  Nitric  Acid.  The 

directions  of  Experiment  1 20  apply  to  rinding  the 
strength  of  a  given  sample  of  nitric  acid  ;  sodium 
nitrate  is  formed. 


Experiments  89 

THE  ALKALI  METALS 

EXPERIMENT  122.  Properties  of  Sodium  and 
Potassium,  (a)  Examine  a  small  piece  of  sodium ; 
note  its  most  obvious  properties,  such  as  color,  luster, 
and  hardness.  Cut  a  slice  off  it  and  immediately  note 
the  metallic  luster.  Review  Experiment  23  (action  of 
sodium  on  water).  Cautiously  dissolve  a  small  piece 
in  a  little  water  in  an  evaporating  dish.  What  is  the 
action  of  the  solution  on  litmus  ?  Evaporate  to  dryness 
and  examine  residue  carefully.  What  is  it  ? 

(b)  Repeat  («),  using"  potassium. 

EXPERIMENT  123.  Preparation  and  Properties  of 
Potassium  Carbonate,  (a]  Fill  a  test  tube  half  full  of 
hardwood  ashes,  cover  with  water,  shake  well  together, 
warm  gently  and  filter.  Test  the  filtrate  (i)  with  both 
blue  and  pink  litmus  paper,  (2)  for  potassium  (Experi- 
ment 127),  and  (3)  for  a  carbonate  (add  HC1 ;  a  result- 
ing effervescence  indicates  CO2). 

(b}  Put  about  5^-  (4^-  circle)  of  cream  of  tartar 
(acid  potassium  tartrate)  in  an  iron  dish  and  heat 
strongly  in  the  hood  until  the  residue  is  white.  Grind 
the  residue  in  a  mortar  with  water,  filter,  and  apply  the 
same  tests  as  in  (a). 

(c)  Mix  thoroughly  about  5^-  (^  cm.  circle)  of  pow- 
dered potassium  nitrate  with  an  equal  bulk  of  powdered 
charcoal,  and  place  the  mixture  in  an  evaporating  dish. 
Heat  an  iron  dish  or  plate  red-hot  and,  standing  at 
arm's  length  and  grasping  the  evaporating  dish  with 
tongs,  pour  the  mixture  upon  the  iron.  If  it  does  not 
deflagrate  at  once,  heat  still  hotter,  being  careful  not 
to  have  your  face  or  hands  above  the  mixture.  When 
deflagration  has  occurred  and  the  product  is  cool,  grind 
it  in  a  mortar  with  a  little  water,  filter,  and  test  the  ni- 
trate as  in  (a}. 


90  Elementary  Chemistry 

EXPERIMENT  124.  Preparation  and  Properties  of 
Sodium  and  Potassium  Hydroxids.  Make  a  solution 
of  about  50 &•  (10  cm-  circle)  of  sodium  carbonate  in  about 
300  c-c.  of  water  and  place  it  in  an  iron  dish.  To  about 
20  ff-  of  lime  add  enough  water  to  slake  it  and  make  a 
milky  mixture,  "milk  of  lime."  Heat  the  sodium  car- 
bonate solution  to  gentle  boiling,  add  the  milk  of  lime 
and  boil  for  five  minutes,  stirring  constantly  with  a  large 
nail  or  a  file.  Let  the  precipitate  settle,  draw  off  a 
little  of  the  clear  liquid  with  a  tube  drawn  out  so  as  to 
form  a  small  pipette, 3  2  transfer  it  to  a  test  tube  and  add 
an  equal  volume  of  dilute  hydrochloric  acid.  If  there 
is  effervescence,  all  of  the  'sodium  carbonate  has  not 
been  changed  into  the  hydroxid  ;  so  add  a  little  more 
milk  of  lime  and  boil.  If  there  is  no  effervescence, 
decant  the  clear  liquid  into  a  beaker.  As  sodium 
hydroxid  attacks  glass  and  porcelain,  it  is  not  advisable 
to  evaporate  the  solution  to  dryness.  The  solution  may 
be  preserved  in  a  rubber-stoppered  bottle,  labeled 
"Sodium  Hydroxid,"  for  use  in  subsequent  work. 

Examine  a  piece  of  commercial  sodium  hydroxid 
and  note  its  most  prominent  physical  properties. 

Potassium  hydroxid  is  to  be  prepared  according  to 
the  same  directions  as  given  for  sodium  hydroxid,  using 
potassium  carbonate  instead  of  sodium  carbonate. 

EXPERIMENT  125.  Preparation  and  Properties  of 
Ammonium  Amalgam.  Put  about  2  c -c-  of  mercury 
into  a  dry  test  tube,  add  a  small  piece  (2  "*»*•)  of  sodium, 
cork  the  test  tube  very  loosely,  and  heat  gently.  As 
soon  as  a  flash  of  light  has  indicated  that  the  sodium 
has  formed  an  amalgam  with  the  mercury,  introduce 
another  piece  of  sodium,  heat,  if  necessary,  as  before, 
and  continue  in  this  way  until  the  amalgam  has  become 
solid.  (An  evaporating  dish  may  be  used  instead  of 
the  test  tube.) 


Experiments  91 

Put  about  ioc-c-  of  a  strong  solution  of  ammonium 
chlorid  in  an  evaporating  dish,  and  introduce  into  it 
about  a  quarter  of  the  sodium  amalgam.  (The  test 
tube  will  probably  have  to  be  broken  to  get  the  amal- 
gam out.)  How  does  the  amalgam  change  ?  Take  up 
some  of  the  substance  in  the  fingers  and  describe  its 
"feel."  What  class  of  substances  give  this  "  feel  "  ? 

Put  the  rest  of  the  sodium  amalgam  into  a  test  tube, 
fill  nearly  full  with  strong  ammonium  chlorid  solution, 
and  when  the  ammonium  amalgam  begins  to  run  out  of 
the  tube,  fill  it  completely  full  with  water,  close  with 
the  thumb  and  invert  over  water.  Try  to  keep  as  much 
of  the  ammonium  amalgam  as  possible  under  the  mouth 
of  the  test  tube  so  that  the  gas  which  forms  may  be 
collected  therein.  When  the  test  tube  is  full,  test  the 
gas.  What  is  it? 

EXPERIMENT  126.  Solvay  Process  of  Sodium  Car- 
bonate Manufacture.  Prepare  saturated  solutions 
(about  100  £•<:•)  of  ammonium  carbonate  and  of  sodium 
chlorid  by  shaking  the  finely  powdered  salts  for  some 
time  with  water.  Decant  the  saturated  solutions  and 
pass  washed  carbon  dioxid  into  the  ammonium  car- 
bonate until  no  more  is  absorbed.  Now  mix  the  two 
solutions,  stir  well,  and  run  in  carbon  dioxid.  If  a  pre- 
cipitate does  not  appear  in  a  few  minutes,  shake  well 
for  some  time,  and  run  in  carbon  dioxid  again.  When 
a  considerable  amount  of  the  precipitate  has  formed, 
prove  it  to  contain  carbon  dioxid  and  sodium  by  appro- 
priate tests. 

EXPERIMENT  127.  Flame  Tests.  Wash  apiece  of 
platinum  wire  as  clean  as  possible  and  then  hold  it  ir> 
a  Bunsen  flame  until  the  latter  is  no  longer  tinged  by 
vt.  Dip  its  end  in  some  sodium  compound  and  bring 
into  the  flame  ;  note  the  color.  Clean  the  wire  again, 
dip  into  some  potassium  compound,  and  hold  in  the 


92  Elementary  Chemistry 

flame.  Unless  the  potassium  compound  is  entirely  free 
from  an  admixture  of  sodium  compounds,  its  character- 
istic color  will  be  masked  by  that  of  sodium.  When  the 
flame  is  observed  through  cobalt  blue  glass,  however, 
as  the  sodium  flame  color  is  absorbed,  that  of  potassium 
alone  is  seen. 

If  a  lithium  salt  is  available,  familiarize  yourself 
with  its  flame  test  also. 

EXPERIMENT  128.  Preparation  and  Properties  of 
the  Nitrates  of  the  Alkali  Metals,  (a)  Put  a  little 
sodium  hydroxid  (or  carbonate)  into  a  dish,  add  a  little 
water,  and  with  constant  stirring  dilute  nitric  acid 
until  a  slightly  acid  reaction,  (litmus  paper)  is  obtained. 
Set  the  dish  aside  and  examine  it  from  day  to  day. 

(b)  Go  through  similar  operations  with  potassium 
hydroxid  or  carbonate  instead  of  sodium. 

(c)  When  crystals  have  formed  from  both  solutions, 
remove  several  specimens  of  each  and  compare  their 
shape  carefully.     Write  a  careful  description  of  each. 
Do  you  now  see  any  reason  for  calling  sodium  nitrate 
cubical  niter,  as  is  sometimes  done  ? 

(d)  Heat  a  few  crystals  of  potassium  nitrate  in  a 
test  tube  until  they  melt  and  effervesce.     Now  drop 
into  the  tube  a  piece  (2  »««•)  of  charcoal.    Describe  what 
happens.     Repeat  with  sulfur  instead  of  charcoal. 

EXPERIMENT  129.  Test  for  a  Nitrate.  Fill  a  small 
test  tube  about  a  fifth  full  of  clear  crystals  of  ferrous 
sulfate  (green  vitriol),  and  then  about  half  full  of  water. 
Shake  until  a  clear  solution  results.  To  this  add  a 
crystal  of  potassium  nitrate  about  the  size  of  a  pin- 
head. 

Fill  another  test  tube  about  a  sixth  full  of  concen- 
trated sulfuric  acid  and,  holding  both  test  tubes  as 
nearly  horizontal  as  possible,  run  the  solution  upon  the 
sulfuric  acid  so  that  the  two  liquids  mix  as  little  as 


Experiments  93 

possible.  The  brown  ring  shown  where  the  solution 
floats  upon  the  acid  indicates  the  presence  of  a  nitrate. 
Make  a  fresh  solution  of  ferrous  sulfate,  and  repeat 
the  test  without  adding1  potassium  nitrate.  Does  the 
brown  ring  appear? 

EQUIVALENT  WEIGHTS 

EXPERIMENT  130.  (Quantitative^)  Equivalent  of 
Sodium.  Weigh  out  to  centigrams  a  piece  of  clean 
lead  foil  about  10  cm-  square.  Cut  off  a  piece  of  sodium 
(about  4mm-  long  and  2mm-  cross  section),  scrape  off 
the  coating  of  oxid  and,  after  wiping  it  dry  on  filter 
paper,  roll  it  into  a  cylindrical  form.  The  weight  of 
this  cylinder  should  be  about  0.9^-.  Carefully  roll  the 
sodium  up  in  the  foil,  leaving  one  end  open,  but  pinch- 
ing the  other  end  tightly  together.  By  this  arrange- 
ment the  exposed  surface  of  the  sodium  alone  can  be 
acted  upon  by  water,  and  the  evolution  of  hydrogen  is 
quite  steady.  Weigh  to  centigrams  the  sodium  and  foil. 
The  weight  of  the  sodium  is  found  by  subtracting  the 
weight  of  the  foil  from  that  of  the  foil  and  sodium. 

Fill  a  500  c-c-  graduated  cylinder  with  water,  close  it 
with  a  piece  of  paper,  and  invert  it  in  a  pneumatic 
trough  containing  only  a  shallow  depth  of  water.  Drop 
the  sodium  wrapped  in  the  foil  in  the  water  and  at  once 
place  over  it  the  inverted  cylinder  to  catch  all  of  the 
escaping  hydrogen.  When  no  more  gas  is  given  off, 
bring  the  water  inside  and  outside  the  cylinder  to  the 
same  level  by  raising  the  cylinder  or  by  pouring  water 
into  the  trough,  and  read  off  the  volume.  Also  read 
the  barometer  and  the  thermometer.  Reduce  the  vol- 
ume to  standard  conditions,  correcting  for  aqueous  ten- 
sion, and  multiply  the  reduced  volume  by  0.09  (the 
weight  of  a  liter  of  hydrogen)  to  find  the  weight  of 
hydrogen  evolved.  The  quotient  obtained  by  dividing 


94  Elementary  Chemistry 

the  weight  of  the  sodium  by  that  of  the  hydrogen  is  the 
equivalent  of  sodium. 

EXPB:RIMENT  131.  (Quantitative^)  Equivalent  of 
Zinc.  I.  Weigh  out  to  centigrams  about  5  &•  of  zinc 
(chemically  pure,  if  possible),  and  put  it  into  a  gas  gen- 
erator provided  with  a  stopcock  funnel.  Connect  the 
generator  with  an  aspirating  bottle  (Fig.  24)  of  at  least 
2  l-  capacity.  Cover  the  zinc  with  a  little  \vater  and 
close  the  stopcock.  The  delivery  tube  is  placed  in  a 
vessel  of  water  with  the  levels  of  the  liquid  in  the  ves- 
sel and  in  the  aspirator  the  same  when  the  delivery 
tube  is  open.  Close  the  delivery  tube  and  place  it  in  a 
tared  bottle  or  beaker  holding  at  least  2  /-. 

Measure  out  with  a  pipette  or  a  graduate  50^-  of 
strong  hydrochloric  acid,  put  a  portion  of  it  in  the  stop- 
cock funnel,  open  the  cock  cautiously  and  let  the  acid 
run  into  the  generator;  be  very  careful  to  prevent  any 
air  being  drawn  into  the  generator.  Add  the  acid  from 
time  to  time  so  as  to  keep  up  a  rapid  evolution  of  the  gas. 

When  no  more  hydrogen  is  given  off,  add  all  of  the 
acid,  if  it  has  not  already  all  been  added,  arrange  the 
aspirating  and  receiving  bottle  so  that  their  water 
levels  are  the  same  and,  opening  the  stopcock,  let  the 
acid  drain  into  the  generator.  Let  the  apparatus  stand 
for  several  minutes  to  come  to  the  temperature  of  the 
room,  and  then  close  the  delivery  tube  and  lift  it  out  of 
the  receiving  vessel.  Weigh  or  measure  the  volume  of 
the  water  expelled  from  the  aspirator  by  the  hydrogen, 
read  the  barometer  and  thermometer,  and  reduce  the 
volume  to  standard  conditions,  allowing  for  aqueous 
tension.  Multiply  this  reduced  volume  by  0.09  (the 
weight  of  a  liter  of  hydrogen)  to  get  the  weight  of  the 
hydrogen  evolved.  Divide  the  weight  of  the  zinc  by 
the  weight  of  the  hydrogen  ;  the  quotient  is  the  equiv- 
alent of  zinc  desired. 


Experiments  95 

EXPERIMENT  132.  (Quantitative^  Equivalent  of 
Magnesium.  The  apparatus  and  operations  are  like 
those  in  Experiment  131  :  about  2?-  of  the  metal  should 
be  taken. 

EXPERIMENT  133.  (Quantitative.}  Equivalent  of 
Zinc.  II.  (Hood.)  Clean,  dry,  and  weigh  to  centi- 
grams an  evaporating  dish,  together  with  a  funnel, 
which,  when  inverted,  fits  securely  into  the  dish.  Put 
3  to  4-?-  of  zinc  (preferably  chemically  pure,  although 
ordinary  or  mossy  zinc  will  do)  in  the  dish,  replace  the 
funnel  and  weigh  to  centigrams.  Support  the  dish  on 
a  ring  of  a  stand,  and  pour  in  beside  the  funnel  a  little 
strong  nitric  acid  so  that  it  can  flow  under  the  funnel 
and  attack  the  zinc.  As  soon  as  the  action  subsides  a 
little,  add  more  acid,  and  continue  in  this  way  until  all 
the  acid  is  dissolved.  Now  evaporate  to  dryness,  using 
a  large  flame.  When  the  contents  of  the  dish  appear 
dry,  gradually  increase  the  heat,  finally  heating  as  hot 
as  possible  for  at  least  five  minutes.  Let  the  dish  cool 
and  weigh  it.  Again  heat  to  redness  for  several  min- 
utes and  weigh,  continuing  in  this  way  until  the  dish 
and  contents  do  not  lose  more  than  3  cs-  on  heating. 

The  substance  remaining  is  zinc  oxid ;  the  zinc 
nitrate  at  first  formed  is  decomposed  by  the  heating. 
How  many  grams  of  zinc  oxid  have  you  obtained? 
How  much  oxygen  has  combined  with  the  zinc  taken  ? 
What  is  the  ratio  of  the  weights  of  the  zinc  and  oxy- 
gen ?  Taking  the  equivalent  of  oxygen  as  8,  what  is 
the  equivalent  of  zinc  as  deduced  from  this  experi- 
ment? 

EXPERIMENT  134.  (Quantitative^  To  Determine 
the  Vapor  Density  of  Alcohol  by  Dumas'  Method. 
Fit  a  clean,  dry  flask  (100  to  250  c-c-)  with  a  one-hole 
rubber  stopper  through  which  is  thrust  a  bit  of  glass 
tubing  with  its  upper  end  drawn  out  to  a  diameter  of 


Elementary  Chemistry 


about  a  millimeter  (Fig.  61),  and  after  rubbing  the 
stopper  with  a  little  vaseline  so  as  to  make  it  fit 
gas-tight,  weigh  the  apparatus  to  centigrams  (or  better, 

milligrams).  Take 
the  temperature  and 
pressure  of  the  air. 

Put  about  20  c-c-  of 
alcohol  into  the  flask 
and  immerse  it  up  to 
its  neck  in  boiling 
water  contained  in  a 
beaker  or  can,  hold- 
ing it  submerged  by 
means  of  a  clamp. 
Take  the  temperature 
of  the  boiling  water. 
When  the  alcohol  has 
almost  all  boiled 
away  bring  a  Bunsen 
flame  to  the  tip  of  the 
glass  tube,  and  as 
soon  as  the  alcohol 
flame  goes  out  (an  in- 
dication that  the  flask 
contains  only  alcohol 
vapor)  seal  off. 

Weigh  the  flask 
again  with  the  same 
degree  of  accuracy  as 
before.  Hold  the  neck  of  the  flask  under  water  and 
with  tongs  or  pinchers  break  off  the  tip  of  the  sealed 
tube.  The  flask  should  promptly  fill  almost  completely 
with  water;  if  it  does  not,  the  experiment  must  be 
repeated.  Weigh  the  flask  thus  filled  with  water,  to 
decigrams  only,  on  a  platform  balance.  The  difference 


Fig.    6l  —  DETERMINING   THE    VAPOR    DENSITY 
OF  ALCOHOL 

A  short  piece  of  rubber  tubing,  closed  by  a  pinch- 
cock,  is  substituted  for  the  glass  tip 


Experiments  97 

between  the  weights  of  the  flask  filled  with  water  and 
with  air  gives  the  weight  of  the  water,  which,  as  one 
cubic  centimeter  of  water  weighs  one  gram,  also  gives 
the  volume  of  the  air  and  of  the  alcohol  vapor. 

The  calculation  of  the  results  are  given  on  page  215 
of  the  text. 

SULFUR  AND  ITS  COMPOUNDS 

EXPERIMENT  135.  Properties  of  Sulfur,  (a)  Re- 
view the  observations  you  made  on  sulfur  in  Experi- 
ments i  and  2. 

(b)  Fill  a  test  tube  nearly  half  full  of  sulfur  and, 
grasping  it  with  a  holder,  heat  it  carefully.    What  is  the 
color  of  the  sulfur  just  after  it  melts  ?     Pour  a  drop  or 
so  into  cold  water  and  compare  the  product  with  the 
original  sulfur  taken.     Heat  the  tube  so  as  to  raise  the 
temperature  of  the  melted  sulfur  gradually,  and  from 
time  to  time  tilt  the  tube.     What  changes  occur  in  its 
color  and  viscosity  ?    Do  you  find  that  at  a  certain  tem- 
perature the  sulfur  becomes  so  viscid  that  you  can  invert 
the  tube  without  the  sulfur  running  out  ? 

Heat  to  boiling.  Pour  the  boiling  sulfur  slowly  and 
in  a  thin  stream  into  cold  water  contained  in  a  dish  or 
beaker,  moving  the  tube  around  so  that  the  sulfur  may 
solidify  in  a  long  spiral  rod.  Examine  the  product, 
especially  as  to  color,  hardness,  and  elasticity.  Put  it 
away  in  the  desk  and  examine  it  from  time  to  time  for 
a  week  or  so.  What  changes  take  place  ? 

(c)  Fill  a  combustion  cup  with  sulfur,  set  it  on  fire, 
and  then  put  the  cup  in  the  bottom  of  a  wide-mouthed 
bottle,  covering  it  with  a  piece  of  cardboard.     When 
the  sulfur  ceases  to  burn,  introduce  a  piece  of  dry  blue 
litmus  paper.     What  change  of  color  ?     Then  put  in  a 
piece  of  wet  blue  litmus  paper  and  note  result. 

(d)  Review  Experiment  7,  I. 


98  Elementary  Chemistry 

NOTE.     Experiment  ij6  must  be  performed  in  the  hood. 

EXPERIMENT  136.  Preparation  and  Properties  of 
Hydrogen  Sulfid.  Place  a  little  ferrous  sulfid  in  a 
test  tube  and  add  some  dilute  sulfuric  acid.  If  a  gas  is 
not  given  off,  heat  gently.  Attach  a  delivery  tube  and 
collect  a  small  test  tube  full  of  the  gas  by  down- 
ward displacement  (Fig.  44).  Ignite  the  gas  and  see  if 
you  can  detect  the  odor  of  burning  sulfur.  Pass  the 
gas  for  several  minutes  into  about  2C-C-  of  strong  nitric 
acid  in  a  test  tube.  When  the  inside  of  the  end  of  the 
delivery  tube  becomes  coated  with  a  yellow  substance, 
substitute  a  new  delivery  tube  and  put  it  into  a  second 
test  tube  filled  with  water.  This  will  yield  a  solution 
of  hydrogen  sulfid.  Rinse  out  the  first  delivery  tube, 
pick  out  some  of  the  deposit  and  by  means  of  appropri- 
ate tests  establish  its  identity. 

Add  some  of  the  hydrogen  sulfid  solution  to  a  little 
dilute  copper  sulfate,  CuSO4,  solution.  Result  ?  Repeat 
with  lead  acetate,  Pb(C2H3O2)2,  solution;  with  cad- 
mium sulfate,  CdSO4,  solution  ;  with  potassium  perman- 
ganate (KMnO4)  solution,  bromin  water,  and  chlorin 
water.  What  is  the  result  in  each  case  ? 

If  copper,  lead,  cadmium,  and  sulfur  are  all  bivalent 
elements,  what  are  the  formulas  of  the  products  ?  Write 
the  equations  for  the  reactions.  Repeat  these  tests, 
delivering  the  hydrogen  sulfid  gas  directly  into  the 
solutions  of  the  salts. 

EXPERIMENT  137.     Preparation  of  Sulfur  Dioxid. 

(a)  By   the    burning  of  sulfur.     Review    Experi- 
ment 2. 

(b)  By  the  decomposition  of  sulfuric  acid  by  copper. 
Put  about  10^-  of   copper  in   a   flask   provided  with  a 
cork  and  delivery  tube  with  interposed  "safety  bottle" 
(Fig.  55),  and  add  about  40 c-c-  of  strong  sulfuric  acid. 
Heat  the  flask  cautiously,  removing  the  flame  when  the 


Experiments  99 

effervescence  may  become  too  brisk,  and  collect  two 
receivers  full  by  downward  displacement.  Cover  the 
bottles  well  and  reserve  for  use  in  Experiment  138. 
Let  the  gas  pass  into  a  beaker  half  full  of  water  for  a 
few  minutes,  so  as  to  prepare  a  solution  of  sulfur  dioxid 
(sulfurous  acid). 

(c)  By  t/ie  action  of  dilute  sulfuric  acid  on  sodium 
sulfite.  Put  a  layer  of  sodium  sulfite  nearly  a  centi- 
meter thick  in  the  bottom  of  a  gas  generator,  barely 
cover  it  with  water,  and  add  through  the  funnel  tube 
from  time  to  time  dilute  sulfuric  acid  so  as  to  keep  up  a 
rapid  evolution  of  gas.  Collect  t\vo  receivers  full  by 
dowrnward  displacement,  cover  them  well  and  reserve 
for  Experiment  138.  Prepare  a  solution  of  sulfur  dioxid 
by  passing  the  gas  into  some  water  in  a  beaker  or  a 
bottle,  and  save  for  Experiment  139. 

EXPERIMENT  138.  Properties  of  Sulfur  Dioxid. 
Bleaching  Action,  Place  in  a  receiver  full  of  sulfur 
dioxid  a  piece  of  moistened  calico,  some  petals  of  a  red 
flower  (carnation),  cover  and  allow  to  stand  for  half  an 
hour  or  so.  What  happens  ?  Remove  the  object  intro- 
duced and  place  it  in  a  dish  containing  very  dilute  sul- 
furic acid.  What  change  in  color  ensues  ? 

Oxidation  by  Nitric  Acid.  Pour  a  few  drops  of 
strong  nitric  acid  into  a  receiver  filled  with  sulfur 
dioxid,  cover  and  move  the  receiver  around  so  that  its 
inside  walls  may  become  moistened  with  the  acid. 
What  visible  evidence  is  there  that  the  nitric  acid  is 
being  reduced  ?  To  prove  that  the  sulfur  dioxid  has 
been  changed  into  the  trioxid  (which  dissolves  in  the 
water  to  form  sulfuric  acid),  rinse  out  the  receiver  with 
a  little  water,  pour  into  a  test  tube  and  add  barium 
chlorid  solution.  The  appearance  of  the  white  precipi- 
tate of  barium  sulfate  indicates  the  presence  of  sulfuric 
acid. 


ioo  Elementary  Chemistry 

EXPERIMENT  139.     Properties  of  Sulfurous  Acid. 

Test  the  action  of  the  solution  of  sulfur  dioxicl  prepared 
in  Experiment  137  on  litmus  paper.  Cautiously  taste 
a  drop  of  it  on  a  stirring  rod.  Pour  some  of  it  into  an 
evaporating  dish,  add  a  few  drops  of  litmus  solution  or 
other  indicator,  neutralize  with  sodium  hydroxid  solu- 
tion and  evaporate  the  solution  to  dryness.  How  can 
you  prove  that  the  white  residue  is  the  salt,  sodium 
sulfite,  Na2SO3? 

Add  a  drop  or  so  of  potassium  permanganate  solu- 
tion to  a  little  sulfurous  acid  in  a  test  tube.  Repeat, 
using  potassium  dichromate  instead  of  permanganate. 
Compare  results. 

EXPERIMENT  140.  Properties  of  Sulfuric  Acid. 
Decomposition  by  /teat :  Place  not  more  than  one  drop 
of  strong  sulfuric  acid  in  a  porcelain  dish  and  heat. 
Heat  generated  on  mixing  with  water :  Pour  a  few 
drops  of  strong  sulfuric  acid  into  a  test  tube  half  filled 
with  water.  Action  of  organic  substances:  Try  the 
action  successively  of  a  few  drops  of  strong  sulfuric  acid 
on  (a)  a  splinter  of  wood,  (/;)  a  piece  of  paper,  (c)  a 
piece  of  colored  cloth,  (d)  a  little  sugar,  (c)  a  little 
starch.  It  may  be  necessary  to  heat  gently  in  the  last 
two  cases. 

PHOSPHORUS 

CAUTION.  All  experiments  with  phosphorus 
should  be  carried  out  with  the  utmost  caution,  as 
the  ready  inflammability  of  the  yellow  modification 
of  the  element  makes  such  experiments  dangerous. 
The  waxy  modification  should  never  be  touched 
with  the  fingers  and  should  be  handled  and  cut 
UNDER  WATER.  At  the  conclusion  of  an 
experiment  all  bits  of  phosphorus  left  over  should 
be  carefully  collected  and  burned. 


Experiments  101 

EXPERIMENT  141.  Physical  Properties  of  Phos- 
phorus. Examine  both  red  and  yellow  phosphorus, 
carefully  noting  their  chief  characteristics.  Put  a  piece 
(3  mm.)  of  yellow  phosphorus  in  a  small  dry  test  tube 
and  add  about  3  c-c-  of  carbon  bisulfid. 

CAUTION.     Be  sure  that  no  flames  are  near. 

Shake  carefully  for  a  minute  or  so.  Pour  the  solu- 
tion, every  bit  of  if,  upon  two  or  three  pieces  of  filter 
paper  laid  on  a  ring  of  a  retort  stand  and  set  the  stand 
back  out  of  the  way. 

While  waiting  for  the  carbon  bisulfid  to  evaporate, 
put  a  pinch  of  red  phosphorus  in  a  small  dry  test  tube, 
add  about  3  c-c-  of  carbon  bisulfid,  shake  for  a  minute  or 
so,  filter  through  a  dry  filter  paper,  catch  the  filtrate  in 
a  watch  glass,  and  allow  to  evaporate  (in  the  hood).  Is 
red  phosphorus  soluble  in  carbon  bisulfid  ?  What  hap- 
pens to  the  solution  of  yellow  phosphorus  poured  on 
the  filter  paper?  How  do  you  account  for  the  result? 

EXPERIMENT  142.  Conversion  of  Red  Phosphorus 
into  Yellow  Phosphorus.  Put  a  pinch  of  red  phos- 
phorus in  the  bottom  of  a  small  ignition  tube7,  hold  the 
tube  horizontally  with  the  tongs,  and  gently  heat  the 
bottom  of  the  tube.  When  nearly  all  the  red  phos- 
phorus has  disappeared,  let  the  tube  cool,  then  make  a 
scratch  just  below  the  deposit  that  has  collected  in  the 
cooler  part  of  the  tube  and  break  the  tube.  Rub  the 
deposit  with  a  glass  rod  or  match  stick.  How  do  you 
know  that  yellow  phosphorus  has  been  formed  ?  Do 
not  neglect  to  heat  both  parts  of  the  tube  to  redness  so 
as  to  burn  up  all  the  phosphorus. 

EXPERIMENT  143.  Preparation  and  Properties  of 
Phosphin.  Fill  a  test  tube  fitted  with  a  two-hole  cork, 
through  which  pass  tubes  as  shown  in  Fig.  62,  about 
one-fourth  full  with  sodium  hydroxid  solution,  and  put 
into  it  a  piece  (4 *»»»•)  of  phosphorus.  Connect  the  tube 


102 


Elementary  Chemistry 


which  dips  into  the  soda  solution  with  the  gas  supply 
and  pass  through  the  apparatus  ordinary  illuminating 
gas  until  the  air  is  expelled.  How  can  you  prove  this 
to  be  the  case?  Shut  off  the  gas  and  gently  heat  the 

contents  of  the  test 
tube,  keeping  the  end 
of  the  delivery  tube 
below  water  in  a  dish. 
How  do  you  account 
for  the  rings  of  smoke 
that  appear  ? 

EXPERIMENT  144. 
Preparation  of  Me- 
taphosphoric  Acid. 
Put  a  little  heap  of 
red  phosphorus  on  a 
piece  of  asbestos 
paper  (or  in  a  porce- 
lain crucible)  set  in  a 
crockery  plate,  ignite 
the  phosphorus  and 
invert  over  it  a  perfectly  dry  wide-rnouthed  bottle. 
When  the  phosphorus  ceases  to  burn  set  the  bottle 
upright.  Pour  a  few  drops  of  cold  water  on  the  phos- 
phorus pentoxid  formed,  noting  any  hissing  noise,  and 
test  the  solution  with  blue  litmus.  Put  the  solution 
into  a  test  tube  and  add  silver  nitrate  solution.  What 
is  the  precipitate  formed  ? 

EXPERIMENT  145.  Preparation  of  Orthophos- 
phoric  Acid.  Put  a  little  (i cm-  circle)  red  phosphorus 
in  an  evaporating  dish,  cover  it  with  nitric  acid,  and 
heat  gently.  When  the  action  has  ceased,  filter,  if  the 
solution  is  not  clear,  and  evaporate  the  filtrate  on  the 
water  bath.  Redissolve  the  sirup  which  remains  in  a 
little  water.  What  is  its  action  on  blue  litmus  paper? 


FlG.    62 CONVENIENT    APPARATUS    FOR    PRE- 
PARING   PHOSPHIN 


Experimen  ts  103 

Add  silver  nitrate  solution  and  note  nature  of  the  pre- 
cipitate of  silver  orthophosphate,  Ag3PO4.  If  the  pre- 
cipitate is  of  a  dark  color,  it  is  evident  that  some  phos- 
phorus acid  was  formed  also.  In  that  case  it  is  well 
to  add  silver  nitrate  solution  to  a  solution  of  commercial 
orthophosphoric  acid. 

EXPERIMENT  146.  Reactions  of  Phosphates.  To 
a  solution  of  sodium  hydrogen  phosphate,  Na2HPO4, 
add  some  calcium  chlorid,  CaCl2,  solution.  The  pre- 
cipitate is  secondary  calcium  phosphate,  CaHPO4. 

Prepare  some  "magnesia  mixture"  by  mixing  a  little 
ammonia  hydroxid  and  ammonium  chlorid  with  magne- 
sium sulfate,  and  add  it  to  a  solution  of  acid  sodium 
phosphate.  The  precipitate  is  magnesium  ammonium 
phosphate,  (NH4)MgPO4. 

ARSENIC   AND   ANTIMONY 

EXPERIMENT  147.  Properties  of  Arsenic.  Note 
the  physical  properties  of  arsenic.  In  what  respects 
does  it  resemble  metals?  Heat  a  small  particle  of  the 
element  on  a  porcelain  crucible  cover,  noting  particu- 
larly any  odor. 

EXPERIMENT  148.  Arsin.  {Marsh's  Test  for  Arsenic.) 
Generate  hydrogen  in  a  generator  provided  with  a  long 
(25cm')  glass  delivery  tube  drawn  out  to  a  jet.  Use 
none  but  chemically  pure  materials.  When  the  air  is 
displaced,  light  the  hydrogen  at  the  tip.  Heat  the  glass 
tube  nearest  the  generator  with  a  Bunsen  flame.  If  a 
deposit  appears  in  the  cold  part  of  the  tube,  the  zinc  or 
sulfuric  acid  is  impure  and  the  experiment  should  be 
discontinued  and  other  materials  used.  If  no  subli- 
mate appears  and  the  hydrogen  burns  with  colorless  or 
slightly  yellow  flame,  and  leaves  no  spot  on  the  bottom 
of  a  porcelain  dish  pressed  down  upon  it  an  instant, 
pour  a  few  drops  of  an  arsenical  solution  down  the 


IO4  Elementary  Chemistry 

funnel  tube.  Heat  the  tube  and  note  the  appearance 
of  sublimate  and  the  color  of  hydrogen  flame.  Press 
the  porcelain  dish  in  the  flame  a  moment  and  add 
a  couple  of  drops  of  sodium  hypochlorite  solution  to 
the  spot. 

Soak  pieces  of  green  paper  in  water  and  test  the 
water  for  arsenic  as  above. 

EXPERIMENT  149.  Arsenic  Trioxid,  Trichlorid, 
and  Trisulfid.  (a)  Mix  a  pinch  of  arsenic  trioxid 
with  an  equal  bulk  of  powdered  charcoal,  put  the 
mixture  in  an  ignition  tube,  and  slip  down  over  it  a 
loosely  fitting  plug  of  charcoal.  With  the  tongs  hold 
the  tube  in  a  flame  so  as  to  keep  the  charcoal  plug  red- 
hot  while  heating  the  mixture  of  charcoal  and  oxid. 
What  is  the  nature  of  the  deposit  that  forms  in  the 
cooler  part  of  the  tube  ?  How  can  you  prove  this 
deposit  to  be  arsenic  ? 

(b)  Heat  carefully  a  pinch  of  arsenic  trioxid  with 
sodium  hydroxid  solution.    Sodium  arsenite,  Na2AsO3, 
is  formed. 

(c)  Boil   a  little  of  the  trioxid  with   concentrated 
hydrochloric  acid.     Result  ?     Dilute  with  an  equal  vol- 
ume of  water.     Arsenic  trichlorid  is  formed. 

(d)  Pass  hydrogen  sulfid  into  the  solution  from  (c). 
What  is  the  color  and  appearance  of  the  precipitate  ? 
Let   the   precipitate   settle,   pour   off   the  supernatant 
liquid,  add  some  ammonium  sulfid  to  the  residue,  warm 
gently,  and  shake  well  for  some  time. 

Soluble  ammonium  sulfo-arsenite,  (  )2AsS3,  is 
formed.  To  a  little  of  this  solution  add  a  slight  excess 
of  hydrochloric  acid.  What  happens  ? 

EXPERIMENT  150.  Arsenic  Acid.  Boil  a  little 
arsenic  with  nitric  acid  for  some  time,  then  add  just 
enough  ammonium  hydroxid  to  effect  neutralization. 
To  part  of  this  solution  add  silver  nitrate  solution,  and 


Experiments  105 

to  another,  "magnesia  mixture."  Compare  results  with 
those  obtained  in  Experiment  146. 

EXPERIMENT  151.  Properties  of  Antimony.  Note 
the  physical  properties  of  various  samples  of  antimony 
that  may  be  available. 

EXPERIMENT  152.  Stibin.  Follow  the  directions 
in  Experiment  148,  substituting  antimony  trichlorid 
(Experiment  153)  for  the  arsenical  solution. 

EXPERIMENT  153.  Antimony  Trioxid,  Trichlorid, 
and  Trisulfid.  (a)  Repeat  Experiment  149  (a),  substi- 
tuting antimony  trioxid  for  arsenic  trioxid,  and  com- 
pare results. 

(b)  Boil  a  little  powdered  antimony  with  sodium 
hydroxid    solution    and    compare    results    with    those 
obtained  in  Experiment  149  (#). 

(c)  Place  some  powdered  antimony  in  a  test  tube 
and  add  about  3  c-c-  of  concentrated  hydrochloric  acid 
and  one  cubic  centimeter  of  concentrated  nitric  acid. 
If  a  reaction  does  not  start  promptly,  warm  a  little,  and 
let  it  continue  for  at  least  ten  minutes.     Then  dilute 
with  five  times  its  bulk  of  water  and,  if  the  solution  is 
not  clear,  filter  it.     Pass  hydrogen  sulfid  into  the  solu- 
tion of  antimony  trichlorid  thus  prepared.     If  a  precip- 
itate does  not  soon  form,  add  more  water.     Treat  the 
precipitate  of  antimony  trisulfid,  Sb2S3,  as  directed  in 
Experiment  149  (c)  and  (d). 

(d)  Heat  some    powdered    antimony  with  concen- 
trated   nitric    acid    and    compare    results    with    those 
obtained  in  Experiment  150. 

BISMUTH 

EXPERIMENT  154.  Properties  of  Bismuth.  Note 
the  physical  properties  of  bismuth.  Try  to  dissolve  a 
bit  of  it  in  (i)  concentrated  hydrochloric  and  (2)  con- 
centrated nitric  acid. 


io6  Elementary  Chemistry 

EXPERIMENT  155.     Reactions  of  Salts  of  Bismuth. 

Place  a  few  small  crystals  of  bismuth  nitrate  in  a  test 
tube,  fill  the  tube  a  quarter  full  with  water,  and  add 
small  amounts  of  concentrated  hydrochloric  acid  until 
a  clear  solution  is  obtained.  Pour  a  few  drops  of  the 
solution  into  water,  nearly  filling-  a  test  tube.  The 
white  precipitate  is  bismuth  subnitrate,  BiONO3.  Pass 
hydrogen  sulfid  through  the  rest  of  the  solution.  Filter 
out  the  bismuth  sulfid,  Bi2S3,  and  treat  with  warm  yel- 
low ammonium  sulfid.  Filter  and  acidify  the  filtrate 
with  hydrochloric  acid.  Compare  the  result  with  Ex- 
periments 149  (d)  and  153  (c).  How  can  sulfid  of  bis- 
muth be  separated  from  those  of  arsenic  and  antimony  ? 

MAGNESIUM 

EXPERIMENT    156.      Properties     of    Magnesium. 

Scrape  a  piece  of  magnesium  wire  or  ribbon  bright  and 
note  its  most  obvious  physical  properties.  Grasp  one 
end  of  a  short  piece  with  tongs  and  hold  it  in  a  Bunsen 
flame.  What  is  the  product  and  what  are  its  properties  ? 
Treat  a  little  magnesium  in  a  test  tube  with  dilute 
hydrochloric  or  sulfuric  acid.  What  gas  is  evolved? 

EXPERIMENT  157.  Reactions  of  Magnesium  Salts. 
To  a  little  magnesium  sulfate  solution  add  sodium  or 
ammonium  carbonate  solution.  Also  add  sodium  or 
ammonium  carbonate  solution  to  magnesium  chlorid 
solution.  Compare  results.  What  are  the  products? 

To  about  5  c-c-  of  magnesium  sulfate  solution  add 
about  one  cubic  centimeter  each  of  ammonium  hydroxid 
and  ammonium  chlorid  solution.  Then  add  disodium 
hydrogen  phosphate  solution.  The  precipitate  is  mag- 
nesium ammonium  phosphate  (NH4)MgPO4. 

EXPERIMENT  158.  Preparation  of  Magnesium 
Sulfate.  Place  about  20  #-  of  magnesite  in  a  beaker 
or  flask  and  add  30  to  40  c-c-  of  dilute  sulfuric  acid.  If 


Experiments  107 

effervescence  is  not  vigorous,  heat  a  little.  When  solu- 
tion is  complete,  filter  and  evaporate  the  filtrate  to 
crystallization  on  a  water  bath.  Pour  off  the  mother 
liquor  from  the  crystals  and  dry  them  by  pressing 
between  folds  of  filter  paper. 

EXPERIMENT  159.  Preparation  and  Properties  of 
Calcium  Oxid  (Lime)  and  Hydroxid  (Slaked  Lime). 
Test  a  piece  of  marble  (12  mm-)  with  wet  red  litmus 
paper.  What  reaction  does  it  show  ?  Support  the  lump 
on  a  frame  of  iron  wire  laid  across  a  ring  of  a  stand, 
and  heat  as  hot  as  possible,  using  two  Bunsen  flames, 
or,  better,  a  blast  lamp.  After  heating  for  about  fifteen 
minutes  remove  the  flames,  and  as  soon  as  the  lump  is 
cold,  test  it  again  with  wet  red  litmus  paper.  What 
change  has  supervened  ? 

Place  the  lump  of  quicklime  in  a  dish  or  saucer  and 
pour  water  upon  it  drop  by  drop  as  long  as  it  is  taken 
up  readily.  Do  not  .add  too  much  water.  Keep  the 
lump  under  observation  for  some  time,  and  note  any 
changes  (heat,  volume,  appearance). 

Put  some  of  this  slaked  lime  in  a  bottle  and  fill  the 
bottle  with  distilled  water.  Shake  up  well,  let  settle, 
and  decant  the  clear  liquid  into  another  bottle,  and 
label  it  "Lime  Water." 

EXPERIMENT  160.  Some  Properties  of  Several 
Calcium  Compounds.  Review  Experiment  67.  Place 
a  piece  of  old  mortar  in  a  test  tube,  add  dilute  hydro- 
chloric acid,  and  identify  the  gas. 

Stir  up  some  (5  cm-  circle)  plaster  of  Paris  with 
enough  water  to  make  a  thick  paste.  Spread  the  paste 
on  a  piece  of  paper  and  lay  on  it  a  coin  covered  with  a 
thin  coating  of  vaseline,  embedding  it  slightly  in  the 
paste.  (Do  not  delay  to  wash  out  the  dish,  as  the 
plaster  of  Paris  is  hard  to  remove  after  it  has  set.) 
Carefully  remove  the  coin  after  the  plaster  has  set  for 


io8  Elementary  Chemistry 

an  hour  or  more.  To  about  2  c-c-  of  a  solution  of  calcium 
salt  (chloric!  or  nitrate)  add  ammonium  or  sodium  car- 
bonate solution.  Repeat,  using  ammonium  oxalate 
solution  instead  of  a  carbonate  solution. 

Try  the  flame  test  (Experiment  127)  with  (i)  cal- 
cium chlorid  and  (2)  calcium  sulfate. 

Review  Experiment  38  for  water  of  crystallization 
of  gypsum. 

EXPERIMENT  161.  Reactions  of  Strontium  and 
Barium  Salts,  (a)  To  a  little  strontium  chlorid  solu- 
tion in  a  test  tube  add  a  few  drops  of  ammonium  car- 
bonate solution.  Also  ascertain  the  reaction  between 
a  solution  of  strontium  chlorid  and  dilute  sulfuric  acid. 

(I?)  Test  solutions  of  barium  chlorid  with  ammonium 
carbonate  and  dilute  sulfuric  acid.  Try  the  flame  tests, 
using  (i)  strontium  chlorid,  (2)  strontium  nitrate,  (3) 
barium  chlorid,  and  (4)  barium  nitrate.  Look  at  the 
flames  through  a  spectroscope  or  through  a  diffraction 
grating,  if  these  instruments  are  at  hand. 

BORON   AND   SILICON 

EXPERIMENT   162.      Preparation    of    Boric    Acid. 

Put  about  2$#-  (7  cm-  circle)  of  borax  in  a  beaker  and 
add  about  iooc-c-  of  water.  Heat  and  stir  until  the 
borax  is  all  dissolved  ;  filter  if  the  solution  is  not  clear. 
To  the  hot  solution  add  enough  strong  hydrochloric 
acid  to  make  it  decidedly  acid  to  litmus  paper.  Allow 
the  solution  to  cool  and  stand  for  some  time.  Then 
filter  off  the  boric  acid  crystals  which  have  formed,  and 
purify  them  by  recrystallization  from  the  smallest  pos- 
sible amount  of  boiling  water. 

EXPERIMENT  163.  Characteristic  Reaction  of 
Boron  Compounds.  Dissolve  a  pinch  of  boric  acid 
in  about  2  c-c-  of  strong  alcohol  contained  in  an  evapo- 
rating dish.  Dip  a  tuft  of  asbestos  into  the  solution 


Experiments  109 

and,  holding  it  with  tongs,  set  the  alcohol  on  fire.  What 
is  the  color  of  the  name  ?  Ignite  the  rest  of  the  solu- 
tion in  the  dish. 

EXPERIMENT  164.  Borax  Bead.  Make  a  small  (less 
than  a  millimeter  in  diameter)  loop  at  the  end  of  a  piece 
of  platinum  wire  by  winding  it  around  the  point  of  a 
lead  pencil.  Heat  it  and  touch  it  to  a  small  lump  (2  »*»*•) 
of  borax.  Then  heat  the  borax  until  a  clear,  glass-like 
bead  is  obtained  in  the  loop.  Bring  the  hot  bead  in  con- 
tact with  a  minute  particle  of  some  cobalt  or  iron  com- 
pound and  heat  in  the  flame.  What  color  is  imparted 
to  the  bead  ? 

EXPERIMENT  165.  Preparation  of  Magnesium  Sil- 
icid  and  of  Silicon  Hydrid.  Mix  well  on  a  piece  of 
paper  equal  parts  (2  cm-  circle)  of  powdered  magnesium 
and  very  fine  sand,  place  the  mixture  in  a  small  test 
tube  and,  grasping  it  with  a  test  tube  holder  or  paper 
and  tongs,  with  its  mouth  pointing  so  that  any  of 
the  substance  which  may  be  projected  from  the  tube 
can  do  no  harm,  hold  it  steadily  in  the  tip  of  a  Bunsen 
flame.  After  the  completion  of  the  reaction  break  the 
test  tube  and  throw  small  portions  of  the  product  (mag- 
nesium silicid)  into  dilute  hydrochloric  acid  contained  in 
an  evaporating  dish  or  beaker.  What  takes  place  ?  What 
compound  of  silicon  is  spontaneously  inflammable  ? 

EXPERIMENT  166.  Preparation  of  Silicic  Acids. 
To  about  5  c-c-  of  a  concentrated  solution  of  "  water 
glass  "  (a  crude  mixture  of  sodium  and  potassium  sili- 
cates) add  in  small  proportions  hydrochloric  acid  until 
the  mixture  is  strongly  acid  to  litmus  paper.  Put  a 
little  of  the  thick,  gelatinous  mass  (a  mixture  of  ortho- 
silicic  and  metasilicic  acids)  on  a  piece  of  platinum  foil, 
evaporate  to  dryness,  and  heat  strongly.  Add  a  drop 
of  water  to  the  white  residue,  and  test  it  with  litmus 
paper.  What  is  the  powder  ? 


no  Elementary  Chemistry 

ZINC 

EXPERIMENT  167.  Properties  of  Zinc.  Ascertain 
the  most  obvious  characteristics  of  as  many  different 
forms  (mossy,  granulated,  powdered,  stick)  of  zinc  as 
possible.  Review  Experiments  18  and  104.  In  Experi- 
ment 1 8  hydrogen  and  zinc  chlorid  were  formed  ;  in 
Experiment  104  hydrogen  and  sodium  zincate. 

EXPERIMENT  168.  Reactions  of  Zinc  Salts,  (a) 
Fill  a  test  tube  about  a  fourth  full  of  zinc  sulfate  or 
chlorid  solution  and  add  a  drop  or  two  of  sodium 
hydroxid  solution.  What  is  the  precipitate  formed  ? 
Now  add  little  by  little  enough  sodium  hydroxid  solu- 
tion to  redissolve  the  precipitate  formed  at  first.  The 
alkalin  solution  contains  sodium  zincate. 

(b)  Fill  a  test  tube  about  a  third  full  of  zinc  sulfate 
solution  and  add  a  drop  of  dilute  hydrochloric  acid. 
What  is  the  reaction  of  the  mixture  (litmus)  ?  Pass  in 
hydrogen  sulfid  for  a  few  minutes.  Result  ?  No\v 
transfer  the  mixture  to  a  beaker  and  add  half  its  vol- 
ume of  ammonium  sulfid.  The  precipitate  is  zinc  sul- 
fid. Test  with  litmus.  What  must  the  reaction  of  a 
zinc  salt  solution  be  in  order  that  the  sulfid  may  be 
precipitated  ? 

EXPERIMENT  169.  Blowpipe  Reactions.  Heat  a 
small  piece  of  zinc  on  charcoal  in  the  oxidizing  flame 
of  a  blowpipe.  Moisten  the  incrustation  with  a  drop 
of  cobalt  nitrate  solution  and  heat  again  in  the  oxid- 
izing flame.  Result? 

CADMIUM 

EXPERIMENT  170.  Properties  and  Reactions. 
Examine  a  piece  of  the  cadmium,  and  note  its  most 
obvious  properties. 

Into  a  dilute  solution  of  cadmium  chlorid  or  sulfate 
pass  hydrogen  sulfid  gas.  The  precipitate  which  forms 


Experiments  1 1 1 

is  cadmium  sulfid,  CdS.  Make  the  solution  acid  by 
adding  a  few  drops  of  hydrochloric  acid.  Is  cadmium 
sulfid  soluble  in  dilute  hydrochloric  acid  ? 

Wash  the  precipitate  by  decantation  and  add  ammo- 
nium sulfid  solution.  Is  the  precipitate  redissolved? 
How  can  cadmium  sulfid  be  distinguished  from  other 
yellow  sulfids? 

Add  sodium  hydroxid  solution  in  excess  to  a  solution 
of  a  cadmium  salt.  Is  the  hydroxid  precipitated  solu- 
ble in  caustic  alkali  solution? 

MERCURY 

EXPERIMENT  171.     Preparation  of  Mercury.     Put 

a  little  cinnabar  near  one  end  of  a  glass  tube  (15"*- 
long)  open  at  both  ends,  and  heat  the  glass  under  the 
cinnabar  strongly,  holding  the  tube  in  a  slanting  posi- 
tion and  rotating  it  constantly.  What  gaseous  products 
are  formed?  What  is  deposited  in  the  cooler  part  of 
the  tube  ? 

Mix  a  pinch  of  mercury  chlorid  with  two  or  three 
times  its  bulk  of  dry  powdered  sodium  carbonate,  and 
heat  the  mixture  in  an  ignition  tube.  Note  the  nature 
of  the  sublimate. 

EXPERIMENT  172.  Mercurous  Nitrate.  Fill  the 
rounded  end  of  a  test  tube  nearly  full  of  mercury,  add 
about  5  c-c-  of  water,  and  then  about  $c-c-  of  concentrated 
nitric  acid.  Let  the  action  go  on  for  an  hour  or  so. 
In  the  meantime  perform  Experiment  173.  Pour  the 
contents  of  the  tube  off  from  any  mercury  that  is  left 
into  a  small  beaker,  dissolve  in  the  least  possible  amount 
of  water  any  crystals  which  may  have  formed,  rinse  out 
the  tube  with  about  2OC-C-  of  water,  put  the  rinse  water 
into  the  beaker,  and  add  one  or  two  drops  of  concen- 
trated nitric  acid,  so  as  to  have  a  clear  solution.  Save 
the  solution  for  Experiment  174. 


H2  Elementary  Chemistry 

EXPERIMENT  173.  Mercuric  Nitrate.  Dissolve 
about  half  as  much  mercury  as  was  used  in  Experiment 
172  in  about  ioc-c-  of  concentrated  nitric  acid.  Dilute 
the  solution  of  mercuric  nitrate  thus  formed  with  an 
equal  volume  of  water. 

EXPERIMENT  174.  Reactions  of  Mercurous  Salts. 
To  2  c-c-  of  mercurous  nitrate  solution  add  hydrogen 
sulfid.  The  precipitate  is  a  mixture  of  mercuric  sulfid 
and  mercury.  Add  to  separate  portions  of  the  solu- 
tion, hydrochloric  acid  and  potassium  iodid  solution, 
respectively.  Add  ammonium  hydroxid  to  the  precipi- 
tate from  hydrochloric  acid.  What  are  the  precipitates  ? 
Put  a  strip  of  zinc  and  of  copper  (or  copper  wire)  into 
portions  of  the  mercurous  nitrate  solution.  In  a  few 
minutes  remove  them  and  rub  them  dry.  What  has 
happened  ?  Rub  a  cent  or  a  dime  with  a  piece  of  paper' 
wet  with  mercurous  nitrate  solution. 

EXPERIMENT  175.  Reactions  of  Mercuric  Salts. 
Pass  hydrogen  sulfid  into  the  mercuric  nitrate  solution. 
The  precipitate  is  mercuric  sulfid,  HgS.  Add  to  sepa- 
rate portions  of  mercuric  nitrate  solution,  hydrochloric 
acid  and  potassium  io^id  solution  (this  drop  by  drop). 
What  are  the  precipitates  ? 

ALUMINUM 

EXPERIMENT  1 76.  Properties  of  Aluminum.  Exam- 
ine as  many  different  forms  of  aluminum  as  are  avail- 
able, also  of  its  alloys  ;  note  their  most  prominent 
physical  features. 

EXPERIMENT  177.  Action  of  Acids  and  Alkalis  on 
Aluminum.  Fill  the  rounded  end  of  a  test  tube  with 
aluminum,  add  about  twice  its  volume  of  concentrated 
hydrochloric  acid,  and  warm  and  test  the  gas  evolved. 

Repeat,  using  sodium  hydroxid  solution  (cf.  Experi- 
ment 27).  The  solution  contains  sodium  aluminate. 


Experiments  113 

EXPERIMENT  178.  Action  of  Mordants.  Soak  a 
piece  of  white  cotton  cloth  in  a  strong  solution  of  cochi- 
neal or  indigo  for  a  minute  or  so  ;  then  wring  it  out  and 
dry  it.  Try  to  wash  out  the  color,  using  soap.  Dip  a 
similar  piece  of  cloth  in  a  solution  of  aluminum  acetate 
and  dry  it.  Then  soak  it  in  the  cochineal  or  indigo 
solution  and  dry  it.  Try  to  wash  out  its  color. 

EXPERIMENT  179.  Alums.  Weigh  out  to  a  decigram 
quantities  of  aluminum  sulfate,  A12(SO4)3  -(-  i8H2O, 
and  potassium  sulfate,  K2SO4,  in  the  ratio  of  their 
molecular  weights,  i.  e.  770  :  137.  Fifteen  grams  of  the 
first  salt  to  3  grams  of  the  last  are  good  working  quan- 
tities. Dissolve  each  in  the  smallest  possible  quantity 
of  boiling  water  in  a  test  tube.  Mix  the  two  solutions 
hot  in  an  evaporating  dish  and  set  aside  to  cool  and  crys- 
tallize. Note  taste  and  form  of  crystals, 

Mix  equal  volumes  of  solutions  of  aluminum  sul- 
fate and  ammonium  sulfate  saturated  at  the  boiling 
temperature.  Set  aside  to  crystallize.  The  product  is 
ammonium  alum. 

NOTE.  Large  crystals  may  be  obtained  by  hanging  a  thread 
or  string  in  the  solution. 

EXPERIMENT  180.  Reactions  of  Aluminum  Com- 
pounds. Add  a  dilute  solution  of  sodium  carbonate 
to  a  dilute  solution  of  alum.  Filter  the  precipitate  and 
wash  it  thoroughly.  Transfer  to  a  test  tube,  cover  it 
with  water,  and  add -hydrochloric  acid.  If  the  precipi- 
tate is  a  carbonate,  there  will  be  effervescence.  Add 
ammonium  sulfid  solution  to  a  solution  of  alum.  Filter 
and  wash  the  precipitate  and,  placing  it  in  a  test  tube, 
add  hydrochloric  acid.  If  the  precipitate  is  a  sulfid, 
hydrogen  sulfid  gas  will  be  evolved. 

To  some  aluminum  sulfate  solution  in  a  test  tube 
add  about  one-fifth  as  much  sodium  hydroxid.  Transfer 


114  Elementary  Chemistry 

about  half  of  the  precipitate  of  aluminum  hydroxid, 
A1(OH)3,  thus  formed  to  another  test  tube,  and  add 
an  excess  of  sodium  hydroxid.  Sodium  aluminate  is 
formed.  Is  it  soluble  ?  To  the  other  half  of  the  pre- 
cipitate add  dilute  hydrochloric  acid.  Compare  results 
with  those  obtained  for  zinc  in  Experiment  168. 

TIN 

EXPERIMENT  181.  Physical  Properties.  Examine 
a  stick  of  tin  and  a  piece  of  tin  foil,  and  note  the  physical 
properties  of  the  metal.  Bend  a  stick  of  tin  when  held 
close  to  the  ear.  What  information  does  your  sense  of 
hearing  give  you  in  regard  to  tin  ? 

EXPERIMENT  182.  Crystallization  of  Tin.  Hold- 
ing a  piece  of  tinplate  by  means  of  tongs,  heat  it  in  a 
flame  until  the  tin  coating  commences  to  melt.  Then 
immediately  plunge  it  into  cold  water.  Rub  it  over 
with  a  piece  of  filter  paper  wet  with  dilute  aqua  regia, 
then  with  paper  wet  with  a  solution  of  a  caustic  alkali. 
Note  the  crystalline  figures  brought  out  by  the  action 
of  the  solvents. 

EXPERIMENT  183.  Action  of  Acids  on  Tin.  Fill 
the  rounded  end  of  a  test  tube  with  granulated  tin,  and 
add  enough  concentrated  hydrochloric  acid  to  fill  the 
test  tube  about  a  sixth  full.  Heat  gently  (in  the  hood) 
until  effervescence  commences  and  regulate  the  heat- 
ing so  as  to  cause  the  hydrogen  to  be  given  off  rapidly. 
When  the  action  is  about  at  an  end,  fill  the  test  tube 
full  of  water,  and  save  the  solution  of  stannous  chlorid 
thus  formed  for  Experiments  184,  185,  and  186.  Put  a 
small  piece  of  tin  in  a  test  tube  and  add  a  little  concen- 
trated nitric  acid.  As  soon  as  the  reaction  begins  set 
the  tube  in  a  bottle  in  the  hood.  The  white  product  is 
metastannic  acid.  Heat  a  little  tin  with  strong  sulfuric 
acid  in  a  test  tube.  Result  ? 


Experiments  1 1 5 

EXPERIMENT  184.  Preparation  of  a  Solution  of 
Stannic  Chlorid.  Fill  a  small  test  tube  about  a  sixth 
full  of  the  stannous  chlorid  solution  prepared  in  Experi- 
ment 183,  and  add  a  little  aqua  regia,  or  add  bromin  in 
small  portions  until  its  color  ceases  to  be  discharged, 
and  boil  to  expel  the  excess  of  acid  or  bromin.  What 
is  the  action  of  the  aqua  regia  or  the  bromin  ?  Preserve 
the  solution  for  use  in  Experiment  185. 

EXPERIMENT  185.  Distinction  Between  Stannous 
and  Stannic  Salts,  (a]  To  a  little  of  the  stannous 
chlorid  solution  prepared  in  Experiment  183  add  a  few 
drops  of  mercuric  chlorid  solution.  Note  the  white 
precipitate  of  mercurous  chlorid,  HgCl.  Add  more  of 
the  mercuric  solution  and  heat  gently.  The  gray  tinge 
imparted  to  the  precipitate  is  due  to  mercury  resulting 
from  the  reduction  of  the  mercurous  chlorid. 

(b)  Add  a  few  drops  of  mercuric  chlorid  solution 
to  some   of  the   stannic   chlorid  solution  prepared  in 
Experiment  184.     What  is  the  result? 

(c)  Saturate  with  hydrogen  sulfid  (i)  a  little  of  the 
stannous  chlorid  solution,  and  (2)  of  the  stannic  chlorid 
solution,  and  compare  results. 

(it)  Neutralize  the  contents  of  each  of  the  test 
tubes  with  ammonium  hydroxid  and  add  yellow  ammo- 
nium sulfid.  Shake  up  the  mixtures  in  each  case  and 
compare  results. 

Take  fresh  portions  of  the  solutions  of  stannous  and 
stannic  chlorid,  and  add  to  each  sodium  hydroxid 
solution,  a  drop  or  two  at  a  time. 

EXPERIMENT  186.  Replacement  of  Tin  by  Zinc. 
Fill  a  test  tube  about  one-fourth  full  of  the  stannous 
chlorid  solution  prepared  in  Experiment  183,  and  fill  up 
with  water.  Put  a  narrow  strip  of  sheet  zinc  in  this 
diluted  solution  and  examine  after  a  little  while.  What 
is  the  appearance  of  the  zinc  ? 

9 


1 1 6  Elementary  Chemistry 

EXPERIMENT  187.  (Quantitative.']  (Hood.)  To 
Determine  the  Equivalent  of  Tin.  Weigh  about 
5.00^-  of  tin  foil  in  an  evaporating  dish.  Put  most  of 
it  on  a  piece  of  paper  and  moisten  what  is  left  in  the 
dish  with  strong  nitric  acid.  When  the  action  slackens, 
put  a  little  more  foil  into  the  dish  and  then  a  little 
more  acid.  Use  as  little  acid  as  possible,  but  be  sure 
that  all  the  tin  is  attacked  and  that  there  is  no  loss  of 
metal  from  spattering. 

Cautiously  evaporate  to  dryness  with  free  flame,  and 
finally  heat  as  hot  as  possible  for  at  least  ten  minutes. 
Weigh  when  it  is  cool,  and  after  moistening  with  the 
acid  heat  again  ;  continue  in  this  way  until  the  weight 
remains  practically  unchanged. 

The  product  is  a  compound  of  oxygen.  Taking  the  equivalent 
of  oxygen  as  7.94,  calculate  that  of  tin.  If  tin  is  quadrivalent 
in  this  compound,  what  is  its  atomic  weight  ?  The  specific  heat 
of  tin  is  0.056  ;  what  is  its  atomic  weight  as  deduced  by  Dulong 
and  Petit's  Rule  ? 

LEAD 
EXPERIMENT   188.     Physical  Properties  of  Lead. 

Examine  as  many  different  samples  of  lead  as  possible. 
Cut  a  piece  of  lead  with  a  knife  and  note  appearance 
of  freshly  cut  surface. 

EXPERIMENT  189.  Deposition  of  Lead  by  Zinc. 
Fill  a  test  tube  nearly  full  of  a  solution  of  lead  acetate 
(about  10  per  cent)  and  put  in  it  a  narrow  strip  of 
sheet  zinc.  Examine  after  an  hour  or  so.  Pour  off  a 
little  of  the  solution  and  test  it  for  zinc. 

To  remove  the  lead  that  may  still  be  present  add 
dilute  sulfuric  acid  to  the  solution.  As  lead  sulfate  is 
not  wholly  insoluble  in  water,  add  an  equal  bulk  of 
alcohol,  in  which  the  sulfate  is  quite  insoluble.  Filter 
off  the  lead  sulfate,  neutralize  the  filtrate  with  ammo- 
nium hydroxid,  and  add  ammonium  sulfid  ;  a  white  pre- 
cipitate of  zinc  sulfid  results.  In  case  all  the  lead  has 


Experiments  117 

not  been  removed  from  solution  by  sulfuric  acid,  the 
precipitate  caused  by  ammonium  sulfid  will  not  be 
white,  but  more  or  less  of  a  blackish  color,  depending 
tipon  the  amount  of  lead  sulfid  also  precipitated.  Hy- 
drogen sulfid  is  a  better  precipitant  of  lead  than  sulfuric 
acid,  and  it  is  possible  to  remove  all  the  lead  by  its  use. 
Acidify  the  solution  with  hydrochloric  acid,  pass  hydro- 
gen sulfid  through  it,  filter,  and  add  ammonium  hydroxid 
and  then  ammonium  sulfid. 

EXPERIMENT  190.  Action  of  Acids  on  Lead. 
Scrape  three  small  pieces  of  lead  bright  and  clean, 
place  them  in  test  tubes  and  cover  with  (i)  nitric,  (2) 
hydrochloric,  and  (3)  sulfuric  acid.  If  no  action  takes 
place  promptly,  heat  to  boiling.  Note  the  nature  of 
any  gaseous  products  and  change  in  the  appearance  of 
the  lead.  If  the  lead  dissolves  in  any  of  the  acids,  let 
the  action  continue  to  completion,  pour  out  the  solution 
into  an  evaporating  dish,  and  set  aside  to  crystallize. 

EXPERIMENT  191.  Preparation  and  Properties  of 
Lead  Monoxid.  Heat  on  charcoal  in  the  oxidizing 
flame  of  a  blowpipe  a  very  small  bit  of  lead,  and  note 
any  vapors  and  incrustation  formed  on  the  charcoal. 
Examine  some  litharge  as  to  its  physical  properties  and 
test  its  solubility  in  nitric,  acetic,  sulfuric,  and  hydro- 
chloric acids,  both  cold  and  hot. 

EXPERIMENT  192.  Preparation  and  Properties  of 
Red  Lead.  Mix  about  2&-  (2cm-  circle)  of  lead  mon- 
oxid  with  about  0.5^-  (2  cm-  circle)  of  powdered  potas- 
sium chlorate  or  nitrate,  and  heat  the  mixture  in  an 
iron  spoon  or  dish.  Note  the  physical  properties  of  the 
product  and  compare  it  with  other  samples  of  red  lead. 
Ascertain  in  what  common  acids  red  lead  is  soluble. 

EXPERIMENT  193.  Preparation  and  Properties  of 
Lead  Dioxid.  Place  about  2  s-  (2  cm-  circle)  of  red  lead 
in  a  test  tube,  add  some  dilute  nitric  acid,  and  heat  to 


iiS  Elementary  Chemistry 

boiling  for  several  minutes.  Filter  and  wash  the  brown 
residue.  Put  a  little  of  it  in  a  test  tube,  add  concen- 
trated hydrochloric  acid,  and  heat  gently.  What  gas 
is  evolved  ?  What  other  peroxid  behaves  with  hydro- 
chloric acid  in  a  similar  manner? 

EXPERIMENT  194.  Reactions  of  Lead  Salts.  Put 
a  little  dilute  solution  of  lead  nitrate  or  acetate  in  six 
separate  test  tubes  and  add  to  one  of  each  the  follow- 
ing reagents,  noting  the  nature  of  the  precipitates : 

(1)  Hydrogen  sulfid. 

(2)  Hydrochloric  acid.    Add  several  times  as  much 
water  and  heat  to  boiling.     What  change  ?     Cool  by 
holding  test  tube  in  running^  water.    What  is  the  nature 
of  the  product  ? 

(3)  Sulfuric  acid. 

(4)  Potassium  iodid  solution. 

(5)  Potassium  dichromate  solution. 

(6)  Sodium    hydroxid   solution  gradually    and    in 
small  portions  until  in  excess. 

EXPERIMENT  195.  Action  of  Water  on  Lead.  Fill 
a  flask  half  full  of  water  and  bubble  the  breath  through 
it  for  some  time  so  as  to  charge  the  water  with  carbon 
dioxid.  Scrape  a  piece  of  lead  bright  and  clean,  put  it 
in  the  flask,  cork,  and  let  stand  for  a  day  or  so.  Then 
test  portions  of  the  water  for  lead  by  Experiment  189. 
If  no  lead  is  found  to  be  present,  let  the  lead  act  on  the 
water  for  a  day  or  so  longer,  or  evaporate  off  most  of  the 
water  and  test  again.  Bear  in  mind  that  the  lead  which 
has  dissolved  may  be  so  slight  that  the  precipitate  of 
lead  sulfid  may  be  so  minute  as  merely  to  tinge  the 
liquid  brown. 

COPPER 

EXPERIMENT  196.  Properties  of  Copper.  Examine 
as  many  different  forms  of  copper  as  are  procurable  ; 
note  their  most  prominent  characteristics.  File  a  piece 


Experiments  119 

of  copper  wire  bright  and  heat  it  red  hot.  What  is  the 
black  coating?  Compare  with  Experiments  22  and  no. 

EXPERIMENT  197.  Precipitate  of  Copper.  Hang 
a  strip  of  zinc  (scraped  clean)  in  a  neutral  solution  of 
copper  sulfate ;  also  in  another  test  tube  containing 
copper  sulfate  solution  suspend  an  iron  nail  filed  bright. 
What  soon  occurs  ? 

EXPERIMENT  198.  Preparation  and  Properties  of 
Cuprous  Oxid.  Dissolve  2  &•  of  copper  sulfate  in  30  c-c- 
of  water  and  add  10^-  of  Rochelle  salt  (sodium  potas- 
sium tartrate)  previously  dissolved  in  20  c-c-  of  water. 
Warm  and  filter.  To  the  filtrate  add  IQC.C.  of  a  dilute 
solution  of  grape  sugar,  and  then  enough  sodium 
hydroxid  solution  to  dissolve  any  precipitate,  and  as 
much  again,  so  as  to  make  the  solution  strongly  alka- 
lin.  Boil  gently  until  a  decided  change  occurs.  Filter 
off  the  cuprous  oxid,  Cu2O,  formed,  dry  it,  and  compare 
with  cupric  oxid,  CuO. 

EXPERIMENT  199.  Reactions  of  Copper  Salts.  To 
a  little  copper  sulfate  add  ammonium  hydroxid  in  excess. 
Then  repeat  with  sodium  hydroxid  instead  of  ammo- 
nium hydroxid.  Heat  a  solution  of  copper  sulfate  to 
boiling  and  add  sodium  hydroxid.  This  precipitate  is 
cupric  oxid,  CuO. 

Review  Experiment  136  for  the  action  of  hydrogen 
sulfid  on  solutions  of  copper  salts. 

Review  Experiment  37  for  water  of  crystallization  in 
copper  sulfate  crystals. 

Dip  a  copper  or  platinum  wire  into  copper  sulfate 
solution,  then  take  it  out  and  heat  it  in  a  Bunsen  flame; 
note  the  color  imparted. 

EXPERIMENT  200.  (Quantitative.)  To  Find  the 
Equivalent  of  Copper.  Clean  some  copper  foil  or 
wire  with  emery  paper  so  that  it  is  bright,  and  weigh 
to  centigrams  3^-  of  it.  Place  the  weighed  copper  in  a 


I2O  Elementary  Chemistry 

small  flask,  barely  cover  it  with  water,  and  add  concen- 
trated nitric  acid  in  small  portions,  allowing  plenty  of 
time  for  the  action  to  cease  before  adding  a  fresh  por- 
tion. When  solution  is  complete,  transfer  the  liquid  to 
a  weighed  evaporating  dish,  being  careful  not  to  lose 
any,  and  rinse  out  the  flask  two  or  three  times  with 
^c.c.  Of  Water,  adding  the  rinsings  to  the  dish. 

Cautiously  evaporate  to  dryncss.  The  blue  com- 
pound is  copper  nitrate,  Cu(NO3)2,  which,  when  heated 
to  a  high  temperature,  decomposes  into  nitric  oxid,  oxy- 
gen, and  copper  oxid,  CuO.  Heat  for  at  least  ten  min- 
utes as  hot  as  possible  even  after  the  decomposition  has 
seemed  complete  and  then  weigh  the  copper  oxid.  Heat 
again  and  so  on  to  constant  weight.  The  equivalent  of 
oxygen  is  7.94;  find  that  of  copper.  Copper  is  bivalent 
in  this  compound.  What  then  is  its  atomic  weight  ? 

SILVER 

EXPERIMENT  201.  Preparation  and  Properties  of 
Silver.  I.  Fill  an  evaporating  dish  a  third  full  of  sil- 
ver nitrate  solution,  and  introduce  a  few  globules  of 
mercury.  Set  the  dish  aside  in  a  safe  place  for  a  couple 
of  days.  The  silver  will  then  be  found  forming  little 
crystals,  usually  attached  to  the  mercury.  Remove  them 
with  steel  forceps  and,  after  washing  them  well,  put 
them  in  a  bottle  labeled  "  Silver." 

II.  Pour  concentrated  nitric  acid  over  a  ten-cent 
piece  in  an  evaporating  dish  or  beaker,  and  when  the 
action  slackens,  add  more  acid.  Toward  the  last,  heat 
may  be  applied.  Add  three  or  four  times  its  volume  of 
water  and  then  hydrochloric  acid  until  all  the  silver  is 
removed  as  silver  chlorid,  AgCl.  Let  this  precipitate 
settle  and  wash  by  clecantation  several  times.  Then 
filter  and  wash  free  from  an  acid  reaction.  Divide  it 
into  two  equal  parts  with  a  knife  or  spatula. 


Experiments  \  2 1 

Place  one  part  in  a  dish,  cover  with  dilute  sulfuric 
acid,  and  add  a  piece  of  zinc.  The  silver  which  collects 
as  a  gray  powder  is  to  be  separated  from  the  zinc, 
washed  and  dried.  It  is  then  to  be  placed  in  a  hollow 
excavation  in  a  piece  of  charcoal  and  heated  with  a 
blowpipe  until  it  fuses  into  a  globule. 

Place  the  second  part  in  a  cavity  in  a  piece  of  char- 
coal, cover  it  with  sodium  carbonate,  and  reduce  it  with 
a  blowpipe  flame.  Scrape  the  minute  globules  together 
and  fuse  them  together  into  a  single  bead. 

EXPERIMENT  202.  Reactions  of  Silver  Salts,  (a) 
Add  a  soluble  chlorid  solution,  such  as  HC1  or  NaCl, 
to  a  solution  of  silver  nitrate.  Boil,  filter,  and  expose 
the  silver  chlorid  to  sunlight.  Result  ? 

(b)  Add  a  potassium  bromid  solution  to  a  solution 
of  silver  nitrate.      Heat  to  boiling,  filter,  and  separate 
the  precipitate  into  two  parts.      To  one  add  sodium 
thiosulfate  solution,  Na2S2O3.      Result?      Expose  the 
other  half  to  light.     Result  ? 

(c)  Add  potassium  iodid  solution   to  silver  nitrate 
solution.      Compare  the  properties   of  the  precipitate 
with  those  of  silver  chlorid  and  bromid  obtained  in  (a) 
and  (b). 

IRON 

EXPERIMENT  203.  Properties  of  Iron.  Examine 
as  many  different  forms  as  possible  of  the  varieties  of 
iron,  note  their  most  obvious  physical  properties,  and 
try  the  action  of  a  magnet  on  each.  Which  becomes 
permanently  magnetized  ?  Introduce  a  pinch  of  iron 
powder  into  a  Bunsen  flame.  What  happens  ?  Review 
Experiments  7,  I.  (;/*);  25,  27,  28,  and  51. 

To  get  "clean"  ferrous  reactions  the  ferrous  solution 
must  not  be  given  a  chance  to  oxidize.  If  the  hydro- 
chloric acid  solution  be  poured  directly  from  the  test 
tube  while  hydrogen  is  still  being  evolved,  there  is  no 


122  Elementary  Chemistry 

danger  of  any  ferric  chlorid  being  present.  Solutions 
of  ferrous  sulfate  prepared  from  the  crystals  nearly 
always  oxidize  a  little  so  that  the  true  ferrous  reaction 
is  obscured  by  the  ferric  reaction. 

EXPERIMENT  204.  Reactions  of  Ferrous  Salts. 
Fill  a  test  tube  about  a  fifth  full  of  iron  (filings  or  small 
brads),  add  enough  dilute  hydrochloric  acid  to  fill  the 
test  tube  nearly  half  full,  and  warm,  if  necessary,  to 
start  the  reaction.  By  appropriate  tests  identify  the 
gas  given  off.  Ferrous  chlorid  is  formed  in  solution. 

(a)  As  soon  as  the  action  has  almost  ceased,  pour  a 
little  of  the  solution  into  some  sodium  or  ammonium 
hydroxid  solution.  Note  the  changes  of  color  in  the 
precipitate  of  ferrous  hydroxid  produced.  To  what 
are  they  due  ? 

(l>)  Add  a  little  of  the  ferrous  chlorid  solution  to  a 
solution  of  potassium  ferricyanid,  and  note  nature  of 
the  precipitate  of  ferrous  ferricyanid  (Turnbull's  blue). 

(<r)  Add  a  third  portion  of  the  chlorid  to  potassium 
ferrocyanid  solution.  Result  ? 

(d)  Add  a  fourth  portion  to  potassium  sulfocya- 
nate  solution,  KCNS.  Result  ?  Save  what  ferrous 
chlorid  is  left  for  Experiment  205. 

EXPERIMENT  205.  Reactions  of  Ferric  Salts.  Add 
more  hydrochloric  acid  to  the  iron  used  in  Experiment 
204  and,  after  the  reaction  has  almost  ceased,  filter  the 
solution  into  a  beaker  and  add  2  c-c-  of  concentrated 
nitric  acid.  Boil  for  a  few  minutes  and  note  any  change 
of  color.  The  solution  now  contains  ferric  chlorid  as 
well  as  ferric  nitrate. 

To  ascertain  whether  the  conversion  of  the  ferrous 
into  the  ferric  state  is  complete  or  not,  put  a  few  drops 
in  a  test  tube  and  add  a  little  potassium  ferrocyanid.  If 
a  blue  precipitate  is  formed,  add  one  cubic  centimeter 
more  nitric  acid  and  boil  again.  Put  a  little  of  this  ferric 


Experiments 


123 


solution  into  each  of  four  test  tubes  and  add  the  four 
reagents  used  in  Experiment  204.  Tabulate  the  results 
of  Experiments  204  and  205  as  follows  : 


Ferrous 

Salt 

Ferric 

Salt 

REAGENT 

Precipitate  or 
Solution 

Color 

Precipitate  or 
Solution 

Color 

NaOH  ..  . 

K3Fe(CN)6__  

K4  Fe(CN)R 

KCNS.... 

How  may  a  ferrous  salt  be  distinguished  from  a 
ferric  ? 

EXPERIMENT   206.      Oxidation   of  Ferrous   Salts. 

Place  a  clear  crystal  or  so  of  ferrous  sulfate  in  a  test 
tube  and  fill  the  tube  half  full  of  water.  Shake  the 
tube  until  the  crystal  has  dissolved. 

(a]  Put  half  of  the  solution  into  another  test  tube, 
add  a  little  hydrochloric  acid,  warm  somewhat,  and  add 
a  few  crystals  of  potassium  chlorate.     Heat  to  boiling 
and  test  for  a  ferric  and  a  ferrous  salt. 

(b)  To  the  rest  of  the  ferrous  sulfate  solution  add 
a  little  sulfuric  acid,  heat  to  boiling,  then  run  in  drop 
by  drop  an  equal  volume  of  concentrated  nitric  acid 
and  boil  for  a  few  minutes.    Test  portions  of  the  result- 
ing solution  for  the  presence  of  ferric  and  ferrous  salts. 

EXPERIMENT  207.  Reduction  of  Ferric  Salts.  To 
a  solution  of  ferric  chlorid  add  a  little  hydrochloric 
acid  and  drop  in  some  iron  so  as  to  give  a  good  evolu- 
tion of  hydrogen.  Add  more  acid,  if  necessary,  to  keep 
up  the  action  for  at  least  a  quarter  of  an  hour,  then 
test  a  little  of  the  solution  for  the  presence  of  a  ferrous 
compound.  If  the  test  is  not  decisive,  continue  the 
reduction  until  it  is ;  be  sure  that  hydrogen  is  given  off 
copiously. 


124  Elementary  Chemistry 

EXPERIMENT    208.     Manufacture    of    Ink.     Mix   a 

strong  solution  of  ferrous  sulfate  with  a  little  of  a  solu- 
tion of  powdered  nutgalls.  What  is  the  color  of  the 
mixture  ?  Does  it  deepen  on  standing  for  a  few  min- 
utes ?  Dip  a  pen  into  it  and  see  how  it  writes.  To  a 
small  portion  of  the  ink  add  some  oxalic  acid  solution. 
What  good  method  does  the  result  suggest  in  regard  to 
removing  ink  stains  ? 

EXPERIMENT  209.  Borax  Bead  Test  for  Iron. 
Touch  a  hot  borax  bead  (Experiment  164)  to  some  iron 
compound  so  that  a  small  portion  is  taken  up  by  it,  and 
heat  in  the  oxidizing  flame  of  a  blowpipe  until  the 
bead  is  colored  a  decided^  yellow.  Then  heat  it  in  the 
reducing  flame  until  it  becomes  green. 

NICKEL 

EXPERIMENT    210.      Reactions    of    Nickel    Salts. 

Make  the  following  tests  on  a  dilute  solution  of  nickel 
sulfate  : 

(a)  Add  sodium  hydroxid  solution,  a  few  drops  at 
first,  then  an  excess,  and  warm. 

(b)  Add  ammonium  sulfid  solution  and  see  if  the 
nickel  sulfid  precipitated  is  soluble  in  hydrochloric  acid. 

(c)  Perform  the  borax  bead  test  in  both  the  oxi- 
dizing and  reducing  flames. 

COBALT 

EXPERIMENT    211.      Reactions    of    Cobalt    Salts. 

Use  a  dilute  solution  of  cobalt  chlorid  or  nitrate,  and 
add  the  reagents  directed  in  Experiment  210. 

EXPERIMENT  212.  Analysis  of  a  Nickel  Coin. 
Put  a  five-cent  "nickel"  in  an  evaporating  dish,  cover 
with  nitric  acid,  and  warm  for  a  few  minutes.  Pour 
the  solution  into  a  beaker  and  dilute  with  an  equal  vol- 
ume of  water.  Add  ammonium  sulfid  solution  to  this 


Experiments  1 2  5 

solution  until  no  more  precipitate  is  formed.  Filter 
(saving-  the  nitrate),  wash  the  precipitate  several  times, 
pierce  a  hole  in  the  apex  of  the  filter  paper,  and  wash 
the  precipitate  through  with  a  little  nitric  acid  into 
a  test  tube.  Heat  until  it  dissolves.  What  is  the  color 
of  the  solution,  and  the  presence  of  what  metal  is 
indicated  by  this  color  ?  To  a  little  of  the  solution  add 
ammonium  hydroxid  to  alkalinity.  What  is  the  effect 
on  the  color  of  the  solution  ?  What  metals  do  these 
tests  show  to  have  been  in  the  coin  ? 

Evaporate  the  first  filtrate  nearly  to  dryness.  What 
is  the  color  of  the  concentrated  solution  ?  The  salts  of 
what  metal  have  this  color  ?  Test  the  solution  with  a 
borax  bead.  What  do  you  conclude  ?  What  is  the 
qualitative  composition  of  a  nickel  coin  ? 

CHROMIUM   AND   MANGANESE 

EXPERIMENT  213.     Reactions   of  Chromic   Salts. 

(a]  Add  a  drop  or  so  of  sodium  hydroxid  solution  to 
2  c-c-  of  a  solution  of  a  chromic  salt  (chromic  chlorid 
or  chrome  alum).  The  precipitate  is  chromic  hydroxid 
Cr(OH)3.  Add  an  excess  of  the  sodium  hydroxid  solu- 
tion and  shake.  Then  heat  to  boiling.  Compare  results 
with  those  obtained  with  zinc  and  aluminum. 

(b)  Add  a  little  and  then  an  excess  of  ammonium 
sulfid  to  a  chromic  solution  and  compare  the  result 
with  that  in  (a).  Does  chromium  form  a  sulfid?  Do 
aluminum  and  zinc  ? 

EXPERIMENT  214.  Borax  Bead  Test  for  Chrom- 
ium. Touch  a  borax  bead  to  a  bit  of  chromium  alum 
and  heat  in  both  oxidizing  and  reducing  flame  of  a 
blowpipe.  The  green  coloration  is  very  characteristic. 

EXPERIMENT  215.  Reduction  of  Chromates  to 
Chromic  Compounds.  To  10  c-c-  of  potassium  dichro- 
inate  solution  add  2  c.c.  each  of  concentrated  hydrochloric 


126  Elementary  Chemistry 

acid  and  of  alcohol,  and  warm  gently.  The  chromate 
is  reduced  to  chromic  chlorid  and  the  alcohol  is  oxi- 
dized to  aldehyde.  Note  the  green  color  characteristic 
of  chromic  compounds  and  the  peculiar  odor  of  the 
aldehyde. 

EXPERIMENT  216.  Properties  of  Chromates.  (a) 
Examine  some  crystals  of  potassium  chromate  and 
potassium  dichromate.  What  is  the  color  of  their  solu- 
tions ? 

(b)  To  a  solution  of  potassium  chromate  add  a 
little  concentrated  hydrochloric  acid.  The  change  of 
color  shows  that  the  chromate  has  been  changed  into 
the  dichromate. 

(V)  To  a  solution  of  potassium  dichromate  add 
potassium  hydroxid  drop  by  drop  until  the  color  changes 
to  yellow,  an  indication  of  the  formation  of  a  chromate. 

(d)  Place  a  little  potassium  dichromate  in  a  test 
tube,  cover  with  concentrated  hydrochloric  acid,  and 
heat  gently.     What  evidence  is  there  that  the  acid  is 
oxidized  ?     Repeat  with  potassium  chromate. 

(e)  To   a   solution   of   ferrous  sulfate  add  a  little 
hydrochloric  acid  and  then  drop  by  drop  a  solution  of 
potassium  dichromate.     Test  a  portion  of  the  solution 
for   ferric   salts    by   means   of    potassium    sulfocyanid 
solution. 

EXPERIMENT  217.  Reactions  of  Manganous  Salts. 
(a)  Add  ammonium  hydroxid  to  a  manganous  solution 
(sulfate  or  chlorid).  The  precipitate  is  manganous 
hydroxid,  Mn(OH)2. 

(b)  Add  ammonium  sulfid  to  a  manganous  solution. 
The  precipitate  is  manganous  sulfid,  MnS.  Divide  it 
into  two  parts  and  add  hydrochloric  acid  to  one  and 
acetic  acid  to  the  other,  then  add  an  excess  of  ammo- 
nium hydroxid  to  each.  What  are  your  conclusions 
regarding  the  solubility  of  manganese  sulfid  ? 


Experiments  127 

EXPERIMENT  218.  Borax  Bead  Test  for  Man- 
ganese. Put  a  little  of  any  manganese  compound  in 
a  borax  bead  and  heat  it  in  the  oxidizing  and  in  the 
reducing  flame  of  a  blowpipe ;  note  the  color  of  the 
bead  in  each  case. 

EXPERIMENT  219.  Oxidation  with  Potassium  Per- 
manganate. Mix  with  a  solution  of  ferrous  sulfate  a 
few  drops  of  sulfuric  acid,  and  add,  drop  by  drop,  a 
solution  of  potassium  permanganate.  How  can  you 
show  that  the  permanganate  oxidizes  the  ferrous  to  the 
ferric  salt  ?  Review  Experiment  43. 

SOME  ORGANIC  COMPOUNDS 

EXPERIMENT  220.  Preparation  and  Properties  of 
Aldehydes.  Formaldehyde.  Put  about  4C-C-  of  methyl 
alcohol  in  a  test  tube  and  set  the  tube  in  a  vertical 
position  in  a  rack  or  bottle.  Make  a  spiral  of  copper 
wire  by  winding  it  around  a  lead  pencil,  slip  the  spiral 
off,  and,  holding  it  with  the  tongs,  heat  it  as  hot  as 
possible.  Quickly  drop  the  heated  spiral  into  the 
methyl  alcohol.  The  pungent  odor  produced  is  due  to 
the  formation  of  formaldehyde  vapor. 

AcetaldeJiyde.  To  about  3^-  of  potassium  dichro- 
mate  solution  in  a  test  tube  add  a  little  concentrated 
hydrochloric  acid  and  a  few  drops  of  ethyl  alcohol. 
Heat  gently.  What  does  the  change  in  color  of  the 
mixture  indicate  ?  Acetaldehyde  is  formed  by  the  oxi- 
dation of  the  alcohol,  and  the  peculiar  odor  is  due  to 
acetaldehyde  vapor  which  is  given  off. 

EXPERIMENT  221.  Preparation  and  Properties  of 
Ethyl  Acetate.  Mix  about  2C-C-  of  ethyl  alcohol  with 
an  equal  volume  of  dilute  acetic  acid  in  a  test  tube,  and 
add  a  half  dozen  or  so  drops  of  concentrated  sulfuric 
acid.  Heat  to  boiling  and  note  the  odor  of  the  ethyl 
acetate  formed. 


128  Elementary  Chemistry 

EXPERIMENT  222.     Preparation  and  Properties  of 

Soap.  Put  loc^-6"-  of  a  10  to  12  per  cent  solution  of 
sodium  hydroxid  in  an  iron  or  tinned  dish.  Add  either 
35^-  of  lard  or  100^-  of  castor  oil,  and  boil  gently  for 
about  half  an  hour.  Then  add  in  small  portions  about 
2$<?-  of  finely  powdered  salt,  NaCl,  and  boil  a  few 
minutes  after  all  the  salt  has  been  added.  When  the 
mixture  is  cool  remove  the  soap  formed. 

What  reaction  does  your  soap  show  when  tested  by 
litmus  paper  ?  Add  dilute  sulfuric  acid  to  a  solution  of 
part  of  your  soap  in  distilled  water  until  no  more  solid 
separates  out.  Remove  the  mixture  of  stearic  and 
palmitic  acids  thus  obtained  and  note  its  physical 
properties. 

Put  2C-C-  of  your  soap  solution  into  two  separate 
test  tubes,  and  add  to  one  a  little  magnesium  sulfate 
solution  and  to  the  other  a  little  calcium  sulfate  solu- 
tion. What  occurs  in  each  case,  and  what  takes  place 
on  boiling  the  mixtures  for  a  minute  or  so  ?  Saturate 
lime  water  with  carbon  dioxid  as  in  Experiment  71 
until  a  clear  solution  of  acid  calcium  carbonate  is 
obtained.  Add  a  little  to  a  soap  solution  and  note 
what  happens  both  before  and  after  boiling  the  mixture. 

EXPERIMENT  223.  Fehling's  Test  for  Sugar.  Dis- 
solve a  little  cane  sugar  in  water,  add  a  few  drops  of 
sulfuric  acid,  and  boil  gently  for  about  five  minutes  so 
as  to  change  the  cane  sugar  into  grape  sugar.  Mix  2C-C- 
each  of  copper  sulfate,  Rochelle  salt,  and  sodium 
hydroxid  solutions  in  a  test  tube  and  heat  to  boiling. 
Add  a  few  drops  of  the  grape  sugar  solution  and  boil 
for  three  minutes.  If  no  decided  change  occurs,  add 
more  sodium  hydroxid  and  more  grape  sugar  and  boil 
again.  The  red  substance  obtained  by  the  reducing 
action  of  the  sugar  on  the  copper  sulfate  precipitate 
obtained  is  cuprous  oxid. 


Experiments  1 29 

EXPERIMENT  224.     Preparation  and  Properties  of 

Oxalic  Acid.  Place  5^"-  of  cane  sugar  in  an  evaporat- 
ing dish,  and  add,  in  portions  of  about  $c-c-,  50^-  °f 
concentrated  nitric  acid  previously  diluted  with  a  tenth 
of  its  volume  of  water.  As  the  sugar  reduces  the  nitric 
acid  with  evolution  of  the  red  fumes  of  nitrogen  per- 
oxid,  the  operation  should  be  conducted  in  the  hood. 
Evaporate  on  a  water  bath  until  the  volume  of  the 
liquid  is  less  than  lo^-.  When  the  solution  cools,  crys- 
tals of  oxalic  acid  separate  out. 

Wash  these  crystals  with  a  little  water  and  note  their 
physical  properties.  Do  not  taste  the  acid,  however,  as 
it  is  poisonous. 

Dissolve  a  crystal  of  potassium  permanganate  in  a 
test  tube  a  third  full  of  water,  and  add  half  as  much 
diluted  sulfuric  acid.  Add  a  few  drops  of  this  solution 
to  a  solution  of  oxalic  acid.  Note  the  change  in  color. 
Add  a  drop  of  ink  to  a  solution  of  oxalic  acid.  Result  ? 

EXPERIMENT  225.  Preparation  and  Properties  of 
Nitrobenzene.  Pour  15  c-c-  of  concentrated  nitric  acid 
into  a  flask  (250  c-c-)  and  add  an  equal  volume  of  con- 
centrated sulfuric  acid.  Cool  the  mixture  by  holding 
the  flask  so  that  tap  water  may  flow  around  its  sides. 
Add,  a  few  drops  at  a  time,  ioc-c-  of  benzene,  shaking 
well  and  cooling  the  mixture  thoroughly  after  each 
addition.  Pour  the  product  into  a  bottle  (1,000  to 
1,500  c-c-)  previously  filled  with  cold  water.  The  oily 
liquid  which  sinks  to  the  bottom  is  nitrobenzene. 

Wash  the  nitrobenzene  free  from  acid  by  running  a 
current  of  water  into  the  bottle  for  some  time,  decant 
as  much  of  the  water  as  possible,  and  then  pour  the  oil 
and  the  remainder  of  the  water  upon  a  wet  filter  paper. 
When  the  water  has  drained  off,  place  a  test  tube  under 
the  funnel,  punch  a  hole  in  the  apex  of  the  filter  paper, 
and  catch  the  nitrobenzene. 


130  Elementary  Chemistry 

To  remove  the  water  which  is  mixed  with  the  oil 
put  a  few  pieces  of  fused  calcium  chlorid  in  the  test 
tube  and  let  stand  for  several  hours.  Note  the  physical 
properties  of  the  nitrobenzene. 

EXPERIMENT  226.  Preparation  and  Properties  of 
Aniline.  Put  10^-  of  nitrobenzene  in  a  flask  (250^-), 
add  20  c-c-  of  water  and  15^"-  of  fine  iron  filings.  Shake 
well  together  and  add  2  c-c-  of  concentrated  hydrochloric 
acid.  Hold  the  flask  in  the  hand  and  move  it  around 
in  a  small  Bunsen  flame  so  as  to  keep  the  contents  well 
agitated.  If  the  effervescence  becomes  too  violent 
remove  the  flask  from  the  flame,  and,  if  needs  be,  cool 
it  by  immersion  in  water.  Continue  the  heating  until 
the  odor  of  nitrobenzene  has  disappeared  or  is  very 
faint.  If  the  effervescence  ceases,  add  a  little  more  acid. 

Now  add  enough  10  per  cent  solution  of  sodium 
hydroxid  to  make  the  mixture  strongly  alkalin  (litmus), 
shake  well,  let  settle  for  some  time,  and  then  decant 
into  a  bottle.  Clean  the  flask  out  (using  concentrated 
hydrochloric  acid,  if  necessary),  and  decant  from  the 
bottle  into  the  flask.  Connect  the  flask  with  a  con- 
denser and  distil  until  the  distillate  no  longer  has  a 
milky  appearance.  The  aniline  distils  with  the  steam 
and  on  standing  for  some  time  settles  out  as  an  almost 
colorless  oil  which  is  heavier  than  water.  Note  its 
physical  properties. 


APPENDIXES 


APPENDIX  A 


QUALITATIVE  ANALYSIS 


INTRODUCTORY 

Qualitative  chemical  analysis  has  to  do  with  the  operations  and 
methods  which  are  employed  in  finding  out  what  elements  and 
radicals  are  contained  in  a  substance  or  mixture  of  substances. 

Qualitative  analysis  consists  mainly  of  the  study  of  the  solu- 
bilities of  substances.  In  the  usual  scheme  of  analysis  the  sub- 
stance to  be  analyzed  is  first  brought  into  solution.  A  solution  of 
a  known  compound  (a  reagent)  is  then  added  to  this  solution,  and 
if  a  precipitate  of  certain  properties  is  formed,  a  definite  conclusion 
may  be  drawn  as  to  the  presence  of  certain  elements  or  radicals 
in  the  original  substance  taken.  Other  known  solutions  are  added 
to  the  filtrate  from  this  precipitate,  and  from  the  formation  of 
additional  precipitates  and  observation  of  their  properties  further 
conclusions  can  be  drawn  as  to  the  composition  of  the  original 
substance 

The  solubilities  of  certain  salts  of  the  commoner  metals  permit 
of  their  classification  into  five  groups,  which  are  usually  given  the 
name  of  the  reagent  which  is  added  to  effect  the  precipitation. 
These  groups  are: 


Precipitated  as  sulfids,  PbS, 
HgS,  CuS,  CdS,  Bi2S3,SnS  or 
SnS2,  Sb2S3,  or  Sb2S5,  As2S3 
or  As2S5,  by  hydrogen  sulfid. 
The  last  three  are  soluble  in 
yellow  ammonium  sulfid,  the 
others  not. 


f         Lead         ] 

Mercury 

(tc  salts) 

II.   Hydrogen 
Sulfid  Group 

Copper 
Cadmium 
Bismuth 

Tin 

Antimony 

A 

lb 


Arsenic 

[i] 


11 


Elementary  Chemistry 


Aluminum    1 

Chromium 

III.  Ammonium 
Sulfid  Grout? 

Iron 
Cobalt 
Nickel 

Manganese 
Zinc 

tated  as  hydroxids,  A1(OH)3, 
Cr(OH)3,  Fe(OH)8,  by  am- 
monium hydroxid.  The  last 
four  are  precipitated  as  sul- 
fids,  CoS,  NiS,  MnS,  ZnS,  by 
j  ammonium  sulfid. 


IV.  Ammonium 
Carbonate 
Group 


Calcium       1  Precipitated    as    carbonates, 
Strontium  CaCO3,  SrCO3,  BaCO3, 

Barium  MgCO3  (soluble  in  NH4C1), 

Magnesium   J  by  ammonium  carbonate. 


V.  Alkali  Metals 


f       Lithium 
I        Sodium 
I     Potassium 
I  Ammonj,um 


Not  precipitated  by  any  com- 
mon reagents. 


I.     HYDROCHLORIC   ACID   GROUP 

METHOD  OF  ANALYSIS 

Add  HC1  a  little  at  a  time  to  the  solution  as  long  as  a  precipi- 
tate (ptt.)  is  formed.  Shake  up  well,  filter,  and  wash  twice  with  a 
little  cold  water.  Punch  a  hole  in  the  apex  of  the  filter  paper  and 
wash  the  precipitate  into  a  beaker.  Boil  the  water  and  filter 
while  hot. 


Residue:  AgCl,  HgCl. 

Wash  with   hot  water  and 
twice  pour  over  it  enough 


Residue: 

Filtrate  : 

Hg-NH2-Cl 
and  Hg. 

AgCl-2NH8 

Acidify  with 

A  black  resi- 

HNO3; a  white 

due  proves  the 

ptt.  proves  the 

presence  of  mer- 

presence  of 

cury. 

silver. 

Filtrate:  PbCl2 
Divide  into  two  portions. 

PORTION  I.  Add  K2Cr.,O7  or 
K2CrO4  ;  a  yellow  ptt.  soluble 
in  NaOH  indicates  the  pres- 
ence of  lead. 

PORTION  II.  Add  KI ;  a  yel- 
low ptt.  soluble  in  hot  water 
and  recrystallizing  in  plates 
on  cooling  proves  the  presence 
of  lead. 


Qualitative  Analysis  iii 

REACTIONS  OF  SOLUTIONS  OF  SILVER,  LEAD,  AND 
MERCUROUS  SALTS 


SILVER 

HC1  precipitates  AgCl,  white,  curdy,  changing  on  exposure  to 
the  light  from  lavender  to  black  ;  soluble  in  NH4OH,  forming 
AgCl  •  2NH3,  from  which  solution  HNO3  reprecipitates  AgCl. 

LEAD 

HC1  precipitates  PbCl2,  white,  flocculent,  soluble  in  hot  water, 
crystallizing  in  long  needles  when  solution  cools. 

H2SO4  precipitates  PbSO4,  white. 

K2Cr2O7  or  K2CrO4  precipitates  PbCrO4,  yellow,  soluble  in 
NaOH. 

Kl  precipitates  PbI2,  yellow,  soluble  in  hot  water,  from  which 
when  cold  it  crystallizes  in  shining  plates. 

H2S  precipitates  PbS,  black,  changed  by  hot  and  moderately 


MERCURY 

HC1  precipitates   HgCl,  white,  changed   by  NH4OH   into  a 
black  mixture  of  HgNH,Cl  and  Hg. 


II.     HYDROGEN   SULFID   GROUP 

METHOD  OF  ANALYSIS 

Warm  the  nitrate  from  the  Hydrochloric  Acid  Group  and  pass 
a  current  of  hydrogen  sulfid  through  it.  Make  sure  that  precipi- 
tation is  complete  by  filtering  a  small  portion,  diluting  the 
nitrate,  and  treating  it  with  H2S  a  few  minutes.  Filter  and  wash 
thoroughly  with  hot  water.  Put  a  small  portion  of  the  precipitate 
in  an  evaporating  dish  ;  add  a  little  ammonium  polysulfid.  If  this 
precipitate  dissolves  completely,  Division  A  is  absent ;  if  not, 
treat  the  remainder  of  the  precipitate  with  ammonium  polysulfid 
and  warm  (not  boil}  for  about  three  minutes  with  occasional 
stirring.  Filter  while  hot  and  proceed  as  indicated  in  table  for 
Division  A. 


IV 


Elementary  Chemistry 


DIVISION  A 

Boil  the  precipitate  in  an  evaporating  dish  with  a  small  amount 
of  a  mixture  of  equal  volumes  of  strong  nitric  acid  and  water 
until  brown  fumes  cease  to  be  given  off  freely.  Dilute  with  a 
little  water  and  filter. 


Filtrate  :  Lead,  Bismuth,  Copper,  Cadmium  Salts. 

Add  a  little  strong  H2SO4  and  evaporate  with 
care  until  dense  white  fumes  appear.    Add  an  equal 


volume  of  dilute  H2SO4  and  filter. 

Boil  with 

a  very  little 

Filtrate  : 

Residue: 

aqua  regia. 

Bismuth,  Copper,  Cadmium  Salts. 

PbS04 

Filter,    boil 
the  filtrate 

Add  NH4OH  until  strongly  alkalin. 

Wash, 

until    chlo- 

A  deep  blue  solution  proves^the  pres- 

warm   the 

rin   is   ex- 

ence of  copper.     A  white  ptt.  indicates 
bismuth.     Filter  and  wash. 

ptt.    with 
ammonium 

pelled,  then 
add   SnCU 

acetate 

and    warm. 

Fil 

Copper,  Ca 
If  copper  is 
absent  : 

trate  : 

dmium  Salts. 
If  copper    is 
present  : 

Precipitate 
Bi  (OH)a  or 

basic    salt 
of  bismuth. 

and  a  few 
drops  of 
HC2H302 
and  filter. 
To  the   fil- 

A gray  or 
black     ptt. 
proves  the 
presence  of 
mercury. 

Make  slight- 
ly acid  with 

Acidify   with 
dil.  HC1  and 

Add    two 
or    three 

trate   add 
K2Cr04   or 

dil.  HCland 

precipitate 

drops    of 

K2Cr2O7. 

treat  with 

with     H2S. 

HC1  to  the 

A    yellow 

H2S. 

Filter    and 

ptt.   in   the 

ptt.  soluble 

A    yellow 

boil   the    ptt. 

funnel   and 

in    NaOH 

ptt.  proves 
the    pres- 

immediately 
with  dilute 

allow    the 
filtrate    to 

proves   the 
presence  of 

ence  of  cad- 

H2S04.    Fil- 

drop into  a 

lead. 

mium. 

ter,  rejecting 

beaker    of 

the    residue. 

water. 

Dilute    the 

A  white 

colorless    fil- 

ptt. proves 

trate  with  an 

the    pres- 

equal volume 

ence  of  bis- 

of water  and 

muth. 

treat    with 

H2S. 

A    yellow 

ptt.   proves 

the    presence 

of   cadmium. 

Residue: 

Mercuric 
Salt. 


Qualitative  Analysis  v 

REACTIONS  OF  SOLUTIONS  OF  MERCURIC,  CUPRIC, 
CADMIUM,  AND  BISMUTH  SALTS 

MERCURY 

II2S  precipitates  HgS,  black,  insoluble  in  hot  and  concentrated 
HNO3,  but  changed  by  prolonged  action  of  that  reagent  into 
Hg(NO3)2-  2  HgS,  white  and  insoluble  in  concentrated  HNO3. 
Both  Hg(NO3)2*  2  HgS  and  HgS  are  changed  by  aqua  regia  into 
sulfur  and  HgCl2,  which  is  soluble.  HgS  is  insoluble  in  (NH4)2S. 

SnCl2  reduces  HgCl2  to  HgCl,  white.  An  excess  of  SnCl2 
reduces  the  HgCl  more  or  less  to  mercury,  which  gives  the  HgCl 
a  darker  color. 

COPPER 

H2S  precipitates  CuS,  black,  changed  by  hot  and  concentrated 
HNO3  into  sulfur  and  Cu(NO3)2,  which  is  soluble.  CuS  is  insol- 
uble in  dilute  H2SO4.  CuS  is  slightly  soluble  in  (NH4)2S. 

NH4OH  precipitates  light  blue  basic  salts,  readily  soluble  in 
excess,  producing  deep  blue  solutions  of  ammonia  cupric  salts,  as 
CuSO2-4NH3. 

CADMIUM 

H2S  precipitates  CdS,  varying  in  color  from  light  yellow  to 
orange  according  to  the  conditions  under  which  precipitation 
takes  place;  easily  soluble  in  concentrated  HC1  or  in  hot  and 
dilute  H,SO4  ;  changed  by  hot  and  concentrated  HNO3  into 
sulfur  and  Cd(NO3)2,  which  is  soluble.  CdS  is  insoluble  in 
(NH4)2S. 

NH4OH  precipitates  Cd(OH)2,  white,  readily  soluble  in  excess, 
producing  ammonia  cadmium  salts,  as  Cd(NO3)2'  4NH3. 

BISMUTH 

H2S  precipitates  Bi2S3,  dark  brown  ;  changed  by  hot  and  con- 
centrated HNO3  into  sulfur  and  Bi(NO3)3,  which  is  soluble.  Bi2S3 
is  insoluble  in  (NH4)2S. 

H4O  added  in  large  proportion  to  solutions  of  bismuth  salts 
which  do  not  contain  too  much  acid,  precipitates  basic  salts,  as 
BiOCl,  (BiO)2SO4,  BiONO3,  etc. 

NH4OH  precipitates  Bi(OH)3  or  a  basic  salt,  white  ;  insoluble 
in  excess  ;  soluble  in  dilute  HC1. 


Elementary  Chemistry 


DIVISION  B 

Slightly  acidify  the  ammonium  sulfid  solution  with  HC1.  [If 
the  precipitate  is  white  it  is  probably  only  sulfur.]  Filter,  reject- 
ing the  filtrate,  as  it  contains  no  metals,  transfer  the  precipitate 
to  a  beaker,  add  a  little  concentrated  HC1,  heat  to  boiling  for  a 
few  minutes,  and  filter. 


Filtrate:     Tin,  Antimony  salts. 
Place  a  bright  iron  wire  or  nail  in  the 
filtrate,  warm  gently,  let  stand  for  fifteen 
minutes,  and  then  filter. 


Filtrate : 

SnCl2 

Add  HgCl2. 
A  white  ptt.  get- 
ting gray  when 
more  of  HgCl2 
is  added  and 
heat  applied, 
proves  presence 
of  tin. 


Precipitate:    Antimony 
(in  metallic  state). 

Wash  thoroughly  and 
transfer  to  a  beaker.  Dis- 
solve in  a  little  cone.  HC1 
to  which  a  few  drops  of 
cone.  HNO3  has  been 
added.  Evaporate  nearly 
to  dryness ;  then  add  a 
large  proportion  of  water. 
The  formation  of  a  white 
ptt.  proves  the  presence  of 
antimony. 

[Proof  may  be  confirmed 
by  passing  H2S  into  solu- 
tion with  formation  of 
orange  ptt.] 


Residue: 

Arsenic  Sulfids. 

Dissolve  in  hot, 
cone.  HN03.  Add 
a  little  of  the  solu- 
tion to  a  test  tube 
nearly  half  full  of  a 
solution  of  ammo- 
nium molybdate, 
and  warm  gently. 

A  yellow  crystal- 
line ptt.  proves  the 
presence  of  arsenic. 
Also  try  the  special 
tests. 


REACTIONS  OF  SOLUTIONS  OF  TIN,  ANTIMONY,  AND 
ARSENIC  SALTS 

TIN  (Stannous) 

H2S  precipitates  SnS,  dark  brown  ;  soluble  in  warm  concen- 
trated HC1 ;  soluble  in  (NH4)2S,  forming  sulfo-stannates,  as 
(NH4)2SnS3,  from  which  a  dilute  acid  precipitates  SnS2,  yellow. 

HgCl2  is  reduced  by  SnCl2  in  HC1  solution  to  HgCl,  white; 
an  excess  of  SnCl2  reduces  some  of  the  HgCl  to  mercury,  which 
imparts  a  darker  color  to  the  precipitate. 

TIN  (Stannic) 

H2S  precipitates  SnS2,  yellow,  from  solutions  not  containing 
too  much  HC1 ;  soluble  in  warm  concentrated  HC1 ;  soluble  in 
(NH4)2S,  forming  sulfo-stannates,  as  (NH4)2SnS3. 


Qualitative  Analysis  vii 

ANTIMONY  (pus) 

H2S  precipitates  Sb2S3,  orange  red  ;  soluble  in  warm,  concen- 
trated HC1 ;  oxidized  by  hot,  concentrated  HNO3,  forming  sulfur 
and  H3SbO4,  which  is  soluble.  Sb2S3  is  soluble  in  (NH4)2S; 
forming  sulfo-antimonates,  as  (NH4)3SbS<l,  from  which  dilute 
acids  precipitate  Sb2S5,  orange  red. 

When  SbCl3  is  added  to  a  large  proportion  of  water,  SbOCl, 
white,  is  produced,  which  is  changed  directly  to  Sb2S3  when 
treated  with  H2S. 

ANTIMONY  (fc) 

H2S  precipitates  Sb2S5,  orange  red,  and  resembling  Sb2S3 
in  its  behavior  toward  most  reagents. 

ARSENIC  (ous) 

H2S  precipitates  As2S3,  lemon  yellow;  almost  insoluble  in 
warm,  concentrated  HC1 ;  oxidized  by  hot  concentrated  HNO3 
to  H3AsO4,  which  is  soluble,  sulfur  being  set  free.  As2S3  is 
soluble  in  (NH4)2S,  forming  sulfo-arsenates,  as  (NH4)3AsS4,  from 
which  HC1  precipitates  As2S5. 

ARSENIC  (tc) 

H2S  precipitates  As2S5,  lemon  yellow,  and  resembling  As2S3 
in  its  behavior  toward  most  reagents.  The  precipitation  takes 
place  slowly  and  is  more  complete  if  the  solution  is  warm,  when 
H2S  reduces  the  arsenic  solution  to  the  arsenious  condition  and 
As2S3  is  precipitated. 

(NH4)2MoO4,  ammonium  molybdate,  added  in  excess  to  a 
solution  of  arsenic  acid  containing  HNO3  precipitates  ammonium 
arseno-molybdate,  yellow.  Precipitation  is  best  obtained  by 
adding  the  arsenic  solution  to  a  small  test  tube  half  full  of 
(NH4)2MoO4.  The  mixture  should  then  be  warmed,  but  should 
not  be  heated  above  70°,  lest  MoO3,  white,  be  precipitated. 

III.    AMMONIUM   SULFID   GROUP 

METHOD  OF  ANALYSIS 

Add  NH4OH  to  slight  alkalinity,  heat  to  boiling,  then  add 
(NH4)2S  in  slight  excess ;  heat  again  to  boiling  and  allow  the 
precipitate  to  settle.  Filter  and  wash  thoroughly  with  hot 
water.  Without  delay  treat  the  precipitate  in  an  evaporating 
dish  with  a  mixture  of  equal  volumes  of  strong  HC1  and  water, 
stirring  well.  Filter  and  wash  immediately. 


Vlll 


Elementary  Chemistry 


Residue: 

Nickel,    Cobalt    Sul- 


Filtrate:  Iron,  Aluminum,  Chromium,  Zinc, 
Manganese  Chlorids. 


rids. 

Expel  any  H2S  which  may  be  present  by 

Test  with   borax 

boiling  and  divide  into  two  unequal  portions. 

bead  ;    blue,    cobalt  ; 

PORTION  I.    Evaporate  the  smaller  portion 

brown,  nickel. 

to  small  bulk,  add  a  little   chlorin  wrater, 

To  detect   one    of 

and  boil  until  excess  of  chlorin  is'  expelled. 

these  metals   in  the 

To  the  cooled  solution  add  KCNS.     A  red 

presence  of  the  other, 

color  proves  the  presence  of  iron. 

dissolve   the  residue 

PORTION  II.     To  the  larger  portion  add 

in  a  little  aqua  regia. 
Filter  and  evaporate 

a  little  cone.  HNO3  and  boil.      Evaporate 
to   small  bulk.     Nearly  neutralize  with 

to  small  bulk.     Heat 
to   boiling  and   add 

(NH4),CO3,  and,  transferring  the  solution 
to  a  flask,  add  five  times  its  volume  of  sus- 

an equal  bulk  of  bro- 
min  water  and  then 

pended  BaCO3.     Shake  the  flask  vigorously 
from  time  to  time  for  half  an  hour  and  then 

of  NaOH.     Boil  vig- 

filter. 

orously    and    add    a 

little    bromin    water 

from   time    to    time. 

Precipitate: 

Filtrate:     Zinc, 

Wash  thoroughly 

Chromium,  Aluminum, 

Manganese  Salts. 

with    boiling    water 

Iron  Hydroxids. 

PORTION  I.      Add 

by  decantation,  filter 
and  boil  the  ptt.  with 
NH4OH  and  NH4C1 

PORTION  I.     Fuse   on 
platinum  foil  with 
Na2CO3andKNO3.    A 

HC2H3O2     and 
then    H  2  S  .      A 
white   ptt.    soluble 

and  filter. 

yellow  product  indicates 

in  HC1  proves  the 

the   presence   of   chro- 

presence ot  %ittc* 

Residue: 

Filtrate: 

mium.     Dissolve  in 

PORTION  II.      Put 

Cobalt 

Nickel. 

water   and   make    acid 

a  very  little  in  an 

[Co(OH)3] 

Test  with 
borax 
bead. 

Treat 
withH2S 
A  black 
ptt.  indi- 

with HC2H3O2.    A  red 
ptt.   with  AgNO3    and 
a   yellow   ptt.    with 
Pb(C2H3O2)2    proves 
the   presence    of  chro- 

evaporating   dish, 
add  1  cubic  centi- 
meter    of    cone. 
H2SO4    and    heat 
until   dense    white 

cates  the 

mium. 

fumes    appear. 

presence 

PORTION  II.     Add  an 

Transfer  the  cooled 

of  nickel. 

equal    bulk    of    solid 

contents    of    the 

v^onnrm 

Na2CO3,  half  as  much 

dish  to  a  test  tube 

with  bo- 

TO  V  Vlf^Q  (\ 

Ba(OH)2,  and  5  cubic 

half  full  of  H2S04, 

I  tiX  IJt-cUl. 

centimeters    of    water. 

add  PbO2,  heat  to 

Boil  two  or  three  min- 

boiling   and   allow 

utes.    Filter,  and  to  the 

to  stand  until  sus- 

filtrate add  NH4C1  and 

pended  matter  set- 

boil for  some  time.     A 

tles.      A    red    or 

white    ptt.  ,    best    seen 

purple    colored  so- 

against   a    dark   back- 

lution   proves    the 

ground,  proves  the 

presence    of  man- 

presence of  aluminum. 

ganese. 

Qualitative  Analysis  ix 

REACTIONS  OF  SOLUTIONS  OF  NICKEL,  COBALT,  IRON, 

MANGANESE,  ZINC,  ALUMINUM,  AND 

CHROMIUM  SALTS 

NICKEL 

NH4OH  in  small  proportion  precipitates  Ni(OH)2,  green;  if 
in  excess,  greenish  blue  basic  salts.  The  precipitates  are  soluble 
in  NH4OH  in  the  presence  of  ammonium  salts.  Both  solutions 
and  precipitates  are  changed  by  (NH4)2S  into  NiS,  black. 

KOH  or  NaOH  precipitates  Ni(OH)2,  green  ;  insoluble  in 
excess.  Ni(OH)2  is  oxidized  by  boiling  with  bromin  water  and 
NaOH  to  Ni(OH)3,  black  ;  when  this  is  boiled  with  NH4OH  and 
NH4C1  it  dissolves. 

(NH4)2S  precipitates  from  neutral  or  alkalin  solutions  NiS, 
black;  somewhat  soluble  in  excess  of  (NH4)2S,  more  readily  in 
the  presence  of  NH4OH,  forming  a  dark  brown  .solution  from 
which  NiS  is  reprecipitated  if  the  solvent  is  removed  by  boiling. 
NiS  is  insoluble  in  cold  and  not  very  dilute  HC1 ;  it  is  changed 
by  aqua  regia  to  free  sulfur  and  NiCl2,  which  dissolves.  NiS  is 
oxidized  by  the  oxygen  of  the  air  to  NiSO4. 

A  borax  bead  is  colored  brown  when  fused  with  a  compound 
of  nickel. 

COBALT 

NH4OH  precipitates  blue  basic  salts  ;  easily  soluble  in  NH4OH 
in  the  presence  of  ammonium  salts.  Both  precipitate  and  solution 
are  changed  by  (NH.^S  into  CoS. 

KOH  or  NaOH  precipitates  from  cold  solutions  a  blue  basic 
salt  which,  when  warmed  with  the  alkali,  changes  to  Co(OH)2, 
pink.  Co(OH)2  is  oxidized  to  Co(OH)3,  black,  by  boiling  with 
bromin  water  and  NaOH.  The  Co(OH)3  is  not  affected  by  boil- 
ing with  NH4OH  and  NH4C1. 

(NH4)2S  precipitates  from  neutral  or  alkalin  solutions  CoS, 
black  ;  insoluble  in  excess  ;  practically  insoluble  in  not  very  dilute 
HC1 ;  attacked  by  aqua  regia,  forming  sulfur  and  CoCl2,  which 
dissolves.  CoS  is  oxidized  by  the  air  to  CoSO4. 

A  borax  bead  is  colored  blue  when  fused  with  a  compound  of 
cobalt. 

IRON  {Ferrous} 

NOTE.  As  ferrous  salts  oxidize  very  readily  to  ferric,  it  is  only 
by  taking  special  precautions  that  a  solution  of  ferrous  salt  can 


x  Elementary  Chemistry 

be  kept  from  oxidizing.  The  solution  of  FeSO4  should  be  heated 
with  iron  filings  and  H2SO4,  when  the  hydrogen  will  reduce  any 
ferric  salt  to  the  ferrous  condition. 

NH4OH  in  neutral  solutions  precipitates  incompletely 
Fe(OH)2,  which  oxidizes  promptly  to  compounds  first  green,  then 
black,  and  finally  reddish  brown  Fe(OH*3.  When  these  precip- 
itates are  treated  with  H2S  they  change  into  FeS,  black. 

KOH  or  NaOH  precipitates  Fe(OH)2,  white,  but  oxidizing  as 
described  above. 

(NH4)2S  precipitates  FeS,  black';  attacked  by  hot  concentrated 
HNO3,  forming  sulfur  and  Fe(NO3)3,  which  dissolves.  FeS  is 
soluble  in  dilute  HC1,  and  on  exposure  to  moist  air  oxidizes  to 
FeSO4,  and  finally  to  a  basic  ferric  sulfate  which  is  brown. 

BaCO3,  shaken  with  a  cold,  neutral,  or  slightly  acid  solution  of 
FeCl2,  does  not  precipitate  a  compound  of  iron.  It  is  most  con- 
venient to  employ  the  BaCCXj  suspended  in  water. 

KCNS,  potassium  sulfocyanate,  produces  no  red  coloration  in 
solutions  of  ferrous  salts. 

Concentrated  HNO3,  or  chlorin  water,  oxidizes  ferrous  to  ferric 
salts  very  promptly  at  the  boiling  temperature. 

IRON  (Ferric} 

NH4OH,  KOH,  or  NaOH,  precipitates  Fe(OH)3,  reddish  brown 
and  gelatinous  ;  changed  by  (NH4)2S  into  FeS,  black. 

BaCO3,  when  shaken  with  a  cold,  neutral,  or  but  slightly  acid 
solution  of  a  ferric  salt,  precipitates  Fe(OH)3  or  a  basic  salt. 

KCNS,  potassium  sulfocyanate,  in  excess,  forms  with  solutions 
of  ferric  salts  a  deep  red  complex  soluble  salt. 

H2S  reduces  acid  solutions  of  ferric  salts  to  the  ferrous  condi- 
tion with  separation  of  sulfur. 

MANGANESE  (pus) 

NH4OH,  KOH,  or  NaOH,  precipitates  Mn(OH)2,  white,  oxi- 
dized quickly  to  dark  brown  compounds.  The  precipitate  is 
changed  to  MnS  by  (NH4)2S. 

(NH4)2S  precipitates  MnS,  pink,  soluble  in  dilute  acids  ;  when 
exposed  to  the  air  it  turns  brown. 

BaCO3,  shaken  with  a  cold,  neutral,  or  slightly  acid  solution  of 
MnCl2,  does  not  precipitate  a  compound  of  manganese. 

Fusion  with  Na2CO3  and  KNO3  oxidizes  manganese  com- 
pounds to  green  salts  of  manganic  acid,  K2MnO4  and  Na2MnO4. 


Qualitative  Analysis  xi 

PbO2,  lead  dioxid,  boiled  with  H2SO4  and  a  little  of  a  man- 
ganese compound,  oxidizes  the  latter  to  permanganic  acid, 
HMnO4,  which  imparts  a  pink  or  purple  color  to  the  solution.  If 
a  chlorid  or  HC1  be  present  in  any  considerable  quantity  it  must 
be  removed  by  evaporating  with  concentrated  H2SO4  until  dense 
fumes  appear. 

ZINC 

NH4OH  produces  in  neutral  solutions  a  partial  precipitation 
of  Zn(OH)2,  white  and  gelatinous ;  soluble  in  ammonium  salts 
producing  double  salts  ;  changed  by  (NH4),S  into  ZnS. 

H2S  precipitates  ZnS,  white,  incompletely  from  neutral  solu- 
tions of  zinc  salts  of  the  inorganic  acids  ;  it  is  soluble  in  most 
dilute  acids,  but  is  only  slightly  soluble  in  acetic  acid,  and 
wholly  insoluble  in  a  solution  containing  an  alkalin  acetate,  as 
NaC2H3O2. 

(NH4)2S  precipitates  ZnS,  white. 

BaCO3,  when  shaken  with  a  cold,  neutral,  or  but  slightly  acid 
solution  of  ZnCl2,  does  not  precipitate  any  compound  of  zinc. 


ALUMINUM 

NH4OH  precipitates  A1(OH)3,  white,  gelatinous;  somewhat 
soluble  in  excess,  the  A1(OH)3  being  reprecipitated  by  heat. 

(NH4)2S  precipitates  A1(OH)3,  as  the  sulfid  is  decomposed  by 
water. 

BaCO3,  when  shaken  with  a  cold,  neutral,  or  slightly  acid  solu- 
tion of  A1C13,  precipitates  A1(OH)3  or  basic  carbonates. 


CHROMIUM 

NH4OH  precipitates  Cr(OH)3,  green,  gelatinous,  difficultly 
soluble  in  excess  and  reprecipitated  by  boiling. 

(NH4)2S  precipitates  Cr(OH)3. 

BaCO3,  when  shaken  with  a  cold,  neutral,  or  but  slightly  acid 
solution  of  CrCl3,  precipitates  Cr(OH)3  or  basic  carbonates. 

Fusion  with  KNO3  and  Na2CO3  oxidizes  chromium  compounds 
to  K2CrO4  and  Na2CrO4,  yellow.  If  the  fused  mass  is  dissolved 
in  water  and  the  solution  acidified  with  acetic  acid,  the  addition 
of  lead  acetate  precipitates  PbCrO4,  yellow. 


Xll 


Elementary  Chemistry 


IV.     AMMONIUM   CARBONATE   GROUP 

(The  Alkalin  Earth  Metals] 

METHOD  OF  ANALYSIS 

To  the  solution  add  NH4C1,  NH4OH,  and  then  (NH4)2CO3. 
Warm,  and  if  a  precipitate  appears,  filter  and  wash. 


Precipitate:     BaCO3,  SrCO3,  CaCO3 

Filtrate  : 

Pour  small  portions  of  warm  acetic  acid  upon  the 

Mg.  salt. 

ptt.,  avoiding  an  excess,  until  it  is  dissolved.     To  a 

AddNH4OH 

small  portion  of  the  solution  add  K2Cr2O7,  and  if  a 

and 

ptt.  appears  add  K2Cr2O7  to  all  of  the  solution,  and 

Na2HPO4. 

warm  and  filter. 

R  u'b      the 

Precipitate  : 

Filtrate  : 

inner  surface 
of   the  test 

BaCrO4 

Sr(C2H302)2,  Ca(C2H302)2 

tube   with   a 
glass  rod.    A 

Dissolve  in 
HC1,    warm 

Make   alkalin  with   NH4OH,  add 
(NH4)2CO3    and  warm.     Filter  the 

crystalline 
ptt.    proves 

the    solution 

ptt.  (if  none  appears,  Sr  and  Ca  are 

the  presence 

and   add   a 

absent),  wash   thoroughly,  and  dis- 

of  magne- 

few drops  of 

solve   on    the    filter  with    the  least 

sium. 

H2S04.      A 

possible  quantity  of  HC1.    Evaporate 

white    ptt. 

just  to  dryness,  dissolve  in  a  little 

(which,  how- 

water, filter  if  not  clear,  and  evapo- 

ever,   may 

rate  to  small  bulk.     Divide  into  two 

appear  yel- 

portions. 

low  from  the 

K2Cr2O7    in 
the  solution) 

PORTION  I 

PORTION  II 

proves   the 

SrCl2 

CaCl2 

presence   of 

Add    a  little 

Add    a    little 

barium. 

CaSO4,  heat  to 

K2SO4  and  heat  to 

boiling,    and    if 

boiling.     If  a  ptt. 

no  ptt.   appears 

forms,  filter  it  off 

at  once  let  stand 

and  to  the  filtrate 

for  at  least  ten 

add   NH4OH  till 

minutes.    A  fine 

alkalin,      then 

white  ptt.  proves 

(NH4)2C2O4    and 

the  presence  of 

warm.      A    white 

strontium. 

ptt.    proves   the 

presence    of  cal- 

cium. 

Qualitative  Analysis  xiii 

REACTIONS  OF  SOLUTIONS  OF  BARIUM,  STRONTIUM, 
CALCIUM,  AND  MAGNESIUM  SALTS 

BARIUM 

Na2CO3  or  (NH4)  CO3  precipitates  from  neutral  or  alkalin 
solutions  BaCO3,  white,  flocculent  at  first,  but  becoming  crystal- 
line when  gently  warmed.  BaCO3  is  very  slightly  soluble  in 
NH4C1;  freely  soluble  in  HC1  and  acetic  acid,  HC2H3O2,  with 
effervescence. 

H2SO5  precipitates  BaSO4,  white,  practically  insoluble  in 
water,  acids,  or  alkalis. 

Na2CO3  or(NH4),CO3  precipitates  SrCO3,  resembling  BaCO3. 

STRONTIUM 

H2SO4  precipitates  SrSO4.  Calcium  sulfate,  although  but 
slightly  soluble  in  water,  is  more  soluble  than  SrSO4,  so  that 
CaSO4  will  precipitate  SrSO4  from  a  concentrated  solution  of  a 
strontium  salt.  Precipitation  is  more  complete  when  the  mixture 
is  warmed  or  when  a  concentrated  solution  of  K2SO4  is  used 
instead  of  the  CaSO4. 

K2CrO4  or  K2Cr2O7  does  not  precipitate  SrCrO4  from  dilute 
solutions  acidified  with  HC2H3O2. 

CALCIUM 

Na2CO3  or(NH4)2CO3  precipitates  CaCO3,  resembling  BaCO3. 

K2CrO4  or  K2Cr2O7  produces  no  precipitate  in  dilute  solutions 
acidified  with  HC2H3O2,  since  CaCrO4  is  soluble  in  both  water 
and  HC2H3O2. 

(NH4)2C264  precipitates  CaC2O4,  white,  crystalline. 

H2SO4  or  a  soluble  sulfate,  as  K2SO4,  precipitates  CaSO4  only 
from  concentrated  solutions,  and  then  but  partially. 

MAGNESIUM 

NH4OH  precipitates  from  neutral  solutions  containing  no 
ammonium  salts  one-half  of  the  magnesium  as  Mg(OH)2.  The 
other  half  unites  with  the  ammonium  salt  which  is  formed  to 
produce  double  salts,  such  as  MgCl2  •  2NH4C1.  These  double 
salts  are  soluble  in  water  and  not  precipitated  by  NH4OH  or 
(NH4)2CO3.  The  object  of  adding  NH4C1  in  the  analysis  is  to 
form  the  double  salt  and  thus  prevent  the  precipitation  of  the 
magnesium. 


XIV 


Elementary  Chemistry 


Na2HPO4  or  NaNH4HPO4  precipitates  from  solutions  of 
double  salts,  such  as  MgCl./  2  NH4C1,  in  the  presence  of  NH4OH, 
MgNH4PO4,  white  and  crystalline.  Crystallization  may  be 
hastened  by  stirring  the  solution  with  a  glass  rod. 


V,     THE  ALKALI  METALS:     AMMONIUM,  SODIUM, 
POTASSIUM 

METHOD  OF  ANALYSIS 

Ammonia.  Put  a  little  of  the  original  substance  in  a  small 
beaker  and  add  NaOH.  Cover  the  beaker  with  a  watch  glass,  on 
the  under  side  of  which  is  placed  a  moistened  piece  of  red  litmus 
paper.  Heat  gently,  but  not  to  boiling.  If  the  litmus  paper 
turns  blue  the  presence  of  ammonia  is  proved. 

Sodium  and  Potassium.  Evaporate  the  filtrate  from  the 
ammonium  carbonate  group  to  dryness  and  heat  until  no  more 
fumes  of  ammonium  salts  are  given  off.  Divide  the  residue  into 
two  portions. 


PORTION  I.  Sodium,  Potas- 
sium Salts. 

Moisten  a  small  portion  with 
HC1,  slip  a  clean  platinum  wire 
into  it  and  introduce  into  the 
Bunsen  flame.  A  yellow  flame 
proves  the  presence  of  sodium  ; 
a  violet  flame  proves  the  pres- 
ence of  potassium. 

If  sodium  is  present,  view 
the  flame  through  a  blue  glass, 
whereby  the  yellow  rays  are 
cut  off,  but  the  violet  allowed 
to  pass. 


PORTION  II.  Potassium,  So- 
dium Salts. 

Dissolve  in  least  possible 
amount  of  water  and  divide  solu- 
tion into  two  portions. 


PORTION  I. 
Add  platinum 
chlorid  solution 
and  keep  under 
observation  for 
some  time.  A 
yellow  ptt. 
proves  pres- 
ence of  potas- 
sium. 


PORTION  II. 
Add  picric  acid 
solution.  A  yel- 
low ptt.  indi- 
cates presence 
of  potassium. 


REACTIONS  OF  SOLUTIONS  OF  AMMONIUM,  POTASSIUM, 
AND  vSoDiUM  SALTS 


When 


AMMONIA 

KOH  or  NaOH  when  warmed  with  an  ammonium  salt  liberates 
ammonia,  which  turns  moist  red  litmus  paper  blue. 

any  ammonium  salts  are  heated  they  break  up  into 


Qualitative  Analysis  xv 

volatile  constituents  so  that  through  heat  ammonia  may  be  sepa- 
rated from  non-volatile  substances. 

SODIUM 

Flame  test.  A  sodium  salt  introduced  into  a  Bunsen  flame  on 
a  platinum  wire  colors  it  an  intense  yellow. 

POTASSIUM 

Platinum  chlorid,  PtCl4,  produces  a  yellow  precipitate. 

Picric  acid  produces  a  yellow  precipitate. 

Flame  test.  A  potassium  salt  introduced  into  a  Bunsen  flame 
on  a  platinum  wire  colors  it  violet.  As  this  color  is  marked  by 
even  a  very  small  proportion  of  sodium,  if  that  element  is  present, 
the  flame  should  be  observed  through  blue  glass,  which  absorbs 
the  yellow  light. 

DETECTION  OF  ACIDS 

I.  BARIUM  CHLORID  GROUP 

Sulfuric  acid,  H.,SO4,  precipitates  BaSO4,  white,  insoluble  in 
HC1. 

In  neutral  solution  phosphoric  acid,  H3PO4,  precipitates 
Ba3PO4,  white,  soluble  in  HC1. 

Sulfurous  acid,  H2SO3,  precipitates  BaSO3,  white,  soluble  in 
HC1  with  evolution  of  SO.,  (odor). 

II.  SILVER  NITRATE  GROUP 

Hydrochloric  acid,  HC1,  precipitates  AgCl ;  white  curds  very 
soluble  in  NH4OH. 

Hydrobromic  acid,  HBr,  precipitates  AgBr,  pale  yellow, 
slowly  soluble  in  NH4OH. 

Hydriodic  acid,  HI,  precipitates  Agl,  yellow,  very  slightly 
soluble  in  NH4OH. 

III.     SPECIAL  TESTS  FOR  SOME  COMMON  ACIDS 
Carbonates.     Most  carbonates  give  up   their  carbon   dioxid 
when  acted  upon  by  HC1  or  HNO3.     (See  Experiment  67.) 

Sulfids.  HC1  evolves  H2S  readily  from  the  sulfids  of  the 
alkali  and  alkalin  earth  metals,  and  from  sulfids  of  magnesium, 
manganese,  zinc,  and  iron;  less  readily  from  those  of  lead,  bis- 
muth, cadmium,  antimony,  tin,  nickel,  and  cobalt ;  from  other 
sulfids  with  difficulty  or  not  at  all. 


xr/i  Elementary  Chemistry 

H2S  blackens  filter  paper  moistened  with  lead  acetate  solution. 

A  sulfid,  when  fused  with  a  small  piece  of  solid  NaOH  on  a 
crucible  cover,  forms  Na2S,  which,  when  moistened  and  placed  on 
a  silver  coin,  gives  a  black  stain  of  Ag2S. 

Ace  fates.  Concentrated  H.,SO4  when  warmed  with  an  acetate 
liberates  acetic  acid,  HC2H3O2,  recognizable  odor.  (See  also 
ethyl  acetate,  Experiment  221.) 

In  neutral  solution  FeCl  gives  a  dark  red  color  to  a  solution 
of  an  acetate. 

Nitrates.    (See  Experiment  129.) 


APPENDIX  B 

THE  METRIC  SYSTEM  OF  WEIGHTS  AND 
MEASURES 

The  metric  system  of  weights  and  measures  is 
employed  in  the  affairs  of  everyday  life  in  most  of  the 
countries  of  continental  Europe,  and  is  almost  exclu- 
sively used  in  science. 

The  fundamental  unit  is  the  meter,  which  is  a  unit 
of  length  a  little  over  a  yard  long.  The  other  units  of 
length  are  derived  from  the  meter  by  successively 
multiplying  and  dividing  it  by  ten.  The  names  of 
these  derived  units  are  indicated  by  prefixes.  Thus, 
the  multiple  prefixes  are  the  Greek  words  for  ten, 
deca-,  hundred,  hecto-,  and  thousand,  kilo-,  and  the  sub- 
multiple  prefixes  are  the  Latin  words  for  ten,  deci-, 
hundred,  centi-,  and  thousand,  milli-. 

The  unit  of  weight  or  mass  is  the  gram,  which  is  the 
weight  of  a  cubic  centimeter  of  water  at  4°.  The  same 
prefixes  as  are  given  above  are  used  in  expressing  the 
names  for  the  multiples  and  sub-multiples  of  the  gram. 

The  unit  of  volume  is  the  liter,  which  is  the  volume 
occupied  by  1,000  cubic  centimeters  (one  cubic  deci- 
meter of  water);  1,000  grams  (one  kilogram)  of  water 
occupies  one  liter  at  4°. 

In  this  system  fractions  must  always  be  expressed 
decimally,  and  only  one  unit  should  be  employed  in 
designating  a  quantity  measured.  Thus,  the  fractions 
%,  y$,  ^A,  etc.,  are  written  0.5,  0.33,  0.75,  and  so  on. 
Also  the  weight  of  an  object  is  not  given  as  nine  grams, 
four  decigrams,  and  six  centigrams,  even  when  abbre- 
viated into  9^-,  4^-,  and  6  ^-,  but  should  be  written  9.46^-. 

[  xvii  ] 


3h 


XV111 


Elementary  Chemistry 


The  relations  between  the  units,  multiples,  and  sub- 
multiples  of  the  metric  system  are  shown  in  the 

TABLE  OF  THE  METRIC  SYSTEM 


Length 

Weight 

Volume 

Notation 

Kilometer 

Kilogram 

Kiloliter 

IOOO. 

Hectometer 

Hectogram 

Hectoliter  

IOO. 

Decameter  _. 

Decagram  

Decaliter  

10. 

METER 

GRAM 

LITER 

i  . 

Decimeter 

Decigram 

Deciliter 

O.  I 

Centimeter 

Centigram  _ 

Centiliter  .  . 

O.OI 

Millimeter 

Milligram.. 

Milliliter  

O.OOI 

It  is  evident  from  the  table  that  10  millimeters  equal 
one  centimeter,  10  centimeters  equal  one  decimeter,  10 
decimeters  equal  one  meter,  10  meters  equal  one  hecto- 
meter, and  10  hectometers  equal  one  kilometer.  Anal- 
ogous statements  are  true  for  the  units  of  weight  and 
volume. 

The  abbreviations  most  often  used  in  this  book  are : 
cm.  for  centimeter ;  c-c-  for  cubic  centimeter  ;  L  for  liter  ; 
and  #•  for  gram. 

The  relations  of  the  weights  and  measures  of  the 
metric  system  to  the  weights  and  measures  commonly 
used  in  English-speaking  countries  are  shown  by  the 

TABLE  OF  METRIC  EQUIVALENTS 


One  meter  

— 

39-37 

inches 

One  kilometer  

— 

0.62 

mile 

One  centimeter  

— 

o  39 

inch 

One  liter 

. 

i  06 

liquid,  quart 

One  gram  

— 

15-43 

grains 

One  kilogram  

— 

2    2 

pounds  (Avoir.) 

One  metric  ton  

— 

2204 

pounds 

One  inch  _  

— 

2.54 

centimeters 

One  mile  

— 

1.61 

kilometers 

One  cubic  inch  

— 

16.39 

cubic  centimeters 

One  liquid  quart  

— 

0-95 

liter 

One  pound  (Avoir.)  

— 

0-45 

kilogram 

One  ounce  

— 

28.35 

grams 

Onfi  o-rflin  fAnoth  "k 

__ 

o  .  06/18 

eram 

APPENDIX  C 


100° 


INSTRUMENTS  FOR  WEIGHING  AND 
MEASURING 

The  Thermometer.  The  thermometer  is  an  in- 
strument for  measuring  temperatures.  Its  action  de- 
pends upon  the  fact  that  liquids  expand 
when  heated,  and  contract  when  cooled. 
The  liquids  in  common  use  are  mercury 
or  alcohol  ;  water  is  not  suitable,  as  it 
freezes  at  too  high  a  temperature. 
Chemical  thermometers  (Fig.  a)  consist 
of  a  glass  tube  with  minute  bore,  which 
is  blown  out  into  a  bulb  at  the  end.  The 
bulb  is  almost  invariably  made  cylindri- 
cal in  shape  so  that  the  thermometer 
may  be  thrust  through  a  cork  closing  a 
flask,  test  tube,  or  bottle,  the  tempera- 
ture of  the  interior  of  which  is  to  be 
found.  Details  as  to  the  making  of  ther- 
mometers cannot  be  gone  into  here,  but 
brief  mention  may  be  made  of  the 
method  employed  in  graduating  the 
instrument. 

The  bulb  is  placed  in  a  dish  filled 
with  melting  ice,  and  the  position  of  the 
liquid  in  the  stem  marked  on  the  glass. 
The  instrument  is  then  placed  in  steam 
issuing  from  water  which  is  kept  briskly 
boiling  under  a  pressure  of  one  atmos- 
phere. The  liquid  expands  much  more  than  does  the 
glass  and  rises  in  the  stem.  This  new  position  is  also 

[xix] 


Fig.  a  — 

THERMOMETERS 


XX 


Elementary  Chemistry 


marked  on  the  glass.  The  portion  of  the  stem  between 
the  points  thus  fixed  is  divided  into  a  certain  number  of 
equal  parts,  the  number  depending"  upon  what  scale  is 
adopted.  The  stem  above  and  below  these  fixed  points 
is  likewise  divided  into  parts  which 
are  equal  to  those  between  the  two 
fixed  points. 

In  the  Centigrade  scale,  which 
is  in  general  use  in  continental 
Europe,  and  in  almost  exclusive 
use  among  scientists,  the  interval 
between  the  temperature  of  melt- 
ing ice  and  boiling  water  is  divided 
into  100  equal  parts  ;  the  lower  tem- 
perature is  set  at  o°  and  the  higher 
at  100°.  The  Centigrade  scale  alone 
is  employed  in  this  book. 

In  the  Fahrenheit  sca/e,  which  is 
in  general  use  in  English-speaking 
countries,  the  interval  between  the 
fixed  points  is  divided  into  180 
equal  parts,  and  the  temperature  of 
melting  ice  is  set  at  32°  and  that  of 
boiling  water  at  212°. 

The  value  of  a  Centigrade  degree 
is  1.8  times  that  of  a  Fahrenheit  de- 
gree, and  32°  Fahrenheit  marks  the 
same  temperature  as  o°  Centigrade. 
To  convert  degrees    C.    into   de- 
grees F.,  multiply  by  1.8  and  add 32.     To  convert  degrees 
F.  into  degrees  C.,  subtract  32  and  divide  by  1.8. 

The  Barometer.  The  barometer  is  used  for  meas- 
uring the  pressure  of  the  atmosphere.  In  its  simplest 
form  it  consists  of  a  straight  glass  tube,  about  a  meter 
long  and  closed  at  one  end.  This  is  completely  filled 


Fig.    & A    SIMPLE 

BAROMETER 


Instruments  for  Weighing  and  Measuring     xxi 

with  mercury,  which  is  boiled  in  the  tube  in  order  to 
drive  out  every  trace  of  air  or  moisture,  and  its  open 
end  then  placed  under  the  surface  of  mercury  in  a  dish 
(Fig.  b).  The  mercury  falls  in  the  tube  to  a  height  of 
about  fj6cm-.  The  liquid  does  not  all  run  out  of  the  tube 
because  the  atmosphere  pressing  down  upon  the  mer- 
cury in  the  dish  pushes  it  up  until  the  weight  of  liquid 
in  the  tube  exactly  balances  the  pressure  of  the  atmos- 
phere. If  for  any  cause  the  pressure  of  the  atmosphere 


Fig.  C A    TRIP    BALANCE 

becomes  greater,  it  will  push  the  mercury  higher  up  in 
the  tube  ;  and  in  a  similar  fashion,  if  the  atmospheric 
pressure  becomes  less,  it  cannot  support  so  long  a  column, 
and  accordingly  the  liquid  in  the  tube  falls  somewhat. 
The  Balance.  The  balance  serves  to  find  the 
weight  of  an  object.  When  the  weight  is  to  be  ascer- 
tained only  to  tenths  of  grams,  the  form  of  balance 
known  as  the  "trip  "  (Fig.  c]  is  excellent.  The  weights 
accompanying  need  have  no  pieces  less  than  5  f-t  as  the 
beam  and  sliding  weight  in  the  front  permit  of  the 
weighing  to  tenths  of  grams  up  to  5  s-. 


XX11 


Elementary  Chemistry 


In  the  quantitative  work  of  this  book,   a  balance 
weighing  to  hundredths  of  grams  at  least  is  required. 

Balances  sensi- 
tive to  a  milli- 
gram are  even 
better,  but  are 
much  more  ex- 
pensive and  must 
be  enclosed  in  a 
glass  case  to  pre- 
vent currents  of 
air  from  making 
them  work  too 
erratically.  Either 
an  equal-armed 

balance  (Fig.  d]  or  an  unequal-armed  one  (Fig.  e)  may 
be  used.  Of  the  former  there  are  numerous  excellent 
makes  on  the  market.  They  require  the  use  of  a  box  of 
weights  contain- 
ing tenths  and 
hundredths  of 
grams. 

The  form  of 
balance  in  Fig.  e 
was  devised  by 
the  author  for  the 
quantitative  work 
of  the  elementary 
chemistry  labor- 
atory. Its  advan- 
tages are  ease  in 
moving  about, 
rapidity  of  weigh- 
ing, and  "  non-losableness  "  of  the  weights,  which  are 
rings  moving  along  the  beam. 


Fig.   e UNEQUAL-ARMED    BALANCE 


Instruments  for  Weighing  and  Measuring    xxiii 


RULES  TO  BE  OBSERVED  IN  WEIGHING 

1.  Always  leave  the  balance  and  weight 
in  a  clean  and  usable  condition. 

2.  Never    handle    Hie    vv  eights    with    the 
fingers  ;   use  forceps. 

3.  Do  not  weigh  anything  but 
metals  (mercury  and  sodium  ex- 
cepted)  en  the  bare  scale  pan. 
Liquids  should  be  weighed  in  a 
dish  or  a  beaker,  the  weight  of 
which  has  already  been  found. 
Solids  should  be  placed  on  a 
piece  of  paper  creased  twice  at  soc-c- 
right  angles  so  as  to  sink  in 
a  little  at  the  center  (Fig.  c). 

Graduated  Vessels.  For  measuring 
rather  large  volumes  of  liquids  graduated 
cylinders  (Figs.  /  and  g)  of 
2$oc-c-  or  50^-  capacity  are 
used.  Volumetric  flasks 
(Fig.  h)  are  also  employed. 
For  measuring  small  vol- 
umes of  liquids  pipettes 
(Fig.  i)  and  burettes  (Fig. 
54,  page  77)  are  used.  Pip- 
ettes are  usually  graduated 
to  deliver  5  c-c-,  ioc-c-t  25^-, 

or  50  c-c-.     In  using  a  pipette,  its  tip  is 

dipped  into   the   liquid,   which   is   then 

sucked   up   nearly    to    the    top    by   the 

mouth,  and  the  upper  opening  quickly 

closed  with  the  finger.    By  lifting  up  the 

fore  finger  so  as  to  let  air  into  the  upper      p.g  fc_VOLU_ 

part  of   the  pipette  the  liquid  may  be       METRIC  FLASK 


Fig.  f—  250^. 

CYLINDER 


XXIV 


Elementary  Chemistry 


made  to  drop  out  until  its  level  comes  even  with  the 
mark  on  the  stem.     The  definite  volume  of  liquid 
thus  measured  may  then  be  delivered  into  the 
vessel  in  which  it  is  to  be  used. 

Burettes  are  usually  graduated  into  tenths  of 
cubic  centimeters  and  may  hold  either  25  c-c-  or 
50  c-c- ;  but  as  sometimes  the  spaces  are  divided 
into  0.2  c-c-,  that  is,  fifths  of  a  cubic  centimeter, 
a  burette  should  be  carefully  examined  before  it 
is  used  in  order  that  it  may  be  read  correctly 
according  to  its  scale  of  division.  They  are 
clamped  vertically  to  a  support  and  rilled  by 
pouring  in  the  liquid.  Enough  liquid  is  allowed 
to  run  out  by  opening  the  clamp  to  drive  out  all 
air  in  the  delivery  tube,\and  then  by  noting  the 
reading  of  the  level  of  the  liquid  in  the  burette, 
the  required  volume  may  be  run  out  into  the 
vessel  being  used. 

A  convenient  stopcock  consists  of  a  glass  bead 
made  from  a  rod  a  little  larger  in  diameter  than 
the  bore  of  the  bit  of  rubber  tubing  attached  to 

the  burette.  This  bead  is 
slipped  into  the  rubber 
tube  between  the  burette  pig.  * 
and  the  delivery  tip.  By PIPETTE 
:B  squeezing  the  rubber  a  little, 
a  channel  is  formed  between  it 
and  the  bead,  through  which  the 
liquid  in  the  burette  may  flow. 
The  size  of  this  channel  can  be 
regulated  with  such  ease  that 
the  liquid  may  be  delivered 
with  great  nicety. 

The  surface  of  liquids  which 
^cvet  glass  is  curved  upward  near 


Fig.  / —  READING  A  BURETTE 

The  correct  reading  is  along.  O. 

Readings  such  as  A  and  B  must 

•not  be  taken 


Instruments  for  Weighing  and  Measuring     xxv 

the  glass  so  that  in  small  tubes  the  surface  is  concave. 
The  name  of  meniscus  has  been  given  to  this  curved 
surface.  The  position  of  a  liquid  surface  with  respect 
to  a  scale  is  always  reckoned  at  the  lowest  point  in  the 
meniscus,  and  the  eye  should  be  placed  so  that  a  line 
passing  from  it  to  the  tube  is  perpendicular  to  the  tube 
(Fig.y).  In  the  case  of  liquids  which,  like  mercury,  do 
not  wet  glass,  the  meniscus  is  convex,  and  readings  are 
taken  at  its  highest  point. 

It  is  a  good  plan  for  the  student  to  determine  the 
capacity  of  his  test  tubes,  beakers,  and  flasks  by  pouring 
water  into  them  from  one  of  the  above  vessels.  Their 
volume  once  determined,  no  time  is  lost  in  ascertaining 
what  size  of  beaker,  flask,  or  test  tube  is  to  be  used  in 
the  experiments  ;  they  may  also  serye  as  rough  and 
ready  measuring  vessels. 


NAME  OF 

ELEMENT 


Aluminum  _ 
Antimony.. 

Argon  

Arsenic 

Barium 

Bismuth 

Boron 

Bromin 

Cadmium  .. 
Calcium 

Carbon 

Chlorin 

Chromium  _ 
Cobalt  ...'.. 

Copper 

Fluorin 

Gold 

Hydrogen . . 

lodin 

Iron 

Lead 

Lithium 

Magnesium 
Manganese. 

Mercury 

Nickel 

Nitrogen 

Oxygen  

Phosphorus  . 

Platinum 

Potassium... 

Silicon 

Silver 

Sodium 

Strontium... 

Sulfur 

Tin .... 

Zinc  .. 


APPENDIX  D 
TABLE  I  —  PHYSICAL  CONSTANTS  < 


Name  of  Discoverer  and 
Date  of  Discovery 


Wohler (1827) 

Basil  Valentine (1460) 

Ramsay  and  Ray  leigh__.(  1894) 
Albert  Magnus (i3th  cent.) 

Davy .(1808) 

Basil  Valentine (i5th  cent.) 

Gay-Lussac  and  Thenard  (1808) 

Balard ..(1826) 

Stromeyer (1841) 

Davy (1808) 

Known  from  earliest  times 

Scheele ...(1774) 

Vauquelin ( 1 797) 

Brand (i?35) 

Known  from  earliest  times 

Moissan (1886) 

Known  from  earliest  times 

Cavendish (1776) 

Courtois (1812) 

Known  from  earliest  times 

Known  from  earliest  times. . 


Liebig  and  Bussy  . , (1830) 

Gahn  and  John (I8o7) 

Known  from  earliest  times 

Cronstedt (1751) 

Rutherford _. (1772) 

Priestley ( 1 774) 

Brand (1674) 

Waston... _. (1750) 

Davy (1807) 

Berzelius (1823) 

Known  from  earliest  times 

Davy (1807) 

Davy (1808) 

Known  from  earliest  times 

Known  from  earliest  times 

1 5th  century 


[  xxvi  ] 


TABLES 

>OME    OF    THE    ELEMENTS 


Atomic  Weights 

Valence 

Melting 
Point 

Boiling 
Point 

Specific 
Gravity  l 

H  =  i 

O  -  ib 

Approxi 
mate 

26  9 
19-3 

•1Q.6 

27.1 
120.2 
TO.  9 

27 

120 
4O 

III. 

Ill,  V 

700  (?) 
440 

-) 
1300  (?) 

2.67 
6.72 

J  '  V 

74-4 

.9  y  v 
75-o 

T-W 

75 

III,  V 

446-457 

Red  heat 

5-69 

36.4 

137-4 

137 

II 

Above  that 
of  cast  iron 

•) 

3-75 

06.9 

208.5 

208 

III,  V 

268 

1700 

9.9 

10.9 

II. 

ii 

III 

In  electric 
furnace 

p 

2.6 

79-36 

79.96 

80 

I 

—7-3 

63 

3.1  (liq.) 

ii.  6 

112.4 

112 

II 

320 

770 

8.72 

39-8 

40.1 

40 

II 

Red  heat 

p 

i.  6-1.  8 

( 

Diamond  3.5 

11.91 

12.00 

12 

IV 

p 

?      \ 

Graphite  2.2 

\ 

Charcoal  1.5 

35-18 

35-45 

35-5 

I 

—  IO2 

—34 

1-33  (liq-) 

5i-7 

52.1 

52 

II,  III 

p 

p 

6-7 

58.56 

59-o 

59 

II 

1800 

p 

8.6 

63.1 

63.6 

63-5 

I,  II 

IO5O 

? 

8.9 

18.9 

19. 

ig 

I 

? 

95  7 

197.2 

197 

III 

1030 

p 

19-3 

l.OOO 

1.008 

I 

I 

—  252.  5 

i 

25.90 

126.85 

127 

I 

114 

1  20 

4-95 

55-5 

55-9 

56 

II,  III 

I  TOO 

p 

7.88 

05-35 

206.9 

207 

II,  IV 

325 

p 

n-37 

6.98 

7-03 

7 

I 

1  80 

p 

o-59 

24.18 

24.36 

24 

II 

750 

1  100 

i-75 

54.6 

55-o 

55 

TI 

7-2 

98.5 

200   0 

200 

j      I 

-38:9 

357 

13-59 

58-3 

58-7 

58.5 

,i 

1600 

p 

8.9 

13-93 

14.04 

H 

III,  V 

—  2O3 

—194 

13-93 

15.88 

16.00 

16 

II 

—  1825 

15.88 

30.77 

31.0 

3i 

III,  V 

44.2 

287] 

Yellow  1.83 
Red        2.21 

93  3 

194-8 

195 

IV 

2000 

p 

21-5 

38.86 

39-15 

39 

I 

62.1 

667 

4.9 

28.2 

28  4 

28 

IV 

Above  cast 
iron 

p 

2-5 

07.  12 

107  93 

108 

I 

IOOO 

p 

10.5 

22.88 

23-05 

23 

I 

97-6 

742 

0-97 

86.94 

87.6 

87 

II 

Red  heat 

p 

2-5 

31.83 

32.06 

32 

IIJV.VI 

II4-5 

448 

2.0 

18.1 

119.0 

119 

II,  IV 

227 

1600 

7-3 

64.9 

65-4 

65 

II 

420 

930 

7-i 

i  Referred  to  water  if  the  element  be  in  a  solid  or  a  liquid  state ;  to 
tydrogen  if  in  a  gaseous  state. 

[  xxvii  ] 


xxviii  Elementary  Chemistry 

TABLE  II — TENSION  OF  WATER  VAPOR 


15° 

12  -itnm. 

21° 

20  gfnm. 

16° 

I7.K  mm. 

2_1C 

222  7#W. 

17°  

14  4/«/tt. 

25° 

27  £>mm. 

18°  

15  ^mm. 

26° 

2Z  omm. 

10° 

1  6  3»/w. 

27° 

26  t;  /#/«. 

20°  . 

ij.^mm. 

28° 

28  I  w«. 

21°  

1  8  ^tnm. 

2Q° 

29  S»im. 

ig  -jmm. 

30° 

v  i.e.  mm. 

TABLE  III  —  SOLUTIONS  TO  BE  PREPARED 

The  figures  in  parentheses  indicate  the  number  of  cubic  centi- 
meters (if  the  substance  is  a  liquid)  and  the  number  of  grams  (if 
the  substance  is  a  solid)  that  are  to  be  dissolved  in  water  ;  the 
solution  should  then  be  diluted  to  one  liter. 


Acetic  acid,  (140)  of  80$  acid. 

Alum  (any  one),  (100). 

Aluminum  chlorid,  (TOO). 

Aluminum  sulfate,  (25). 

Ammonium  carbonate.  Dis- 
solve 2oo<?"-  in  a  mixture  of 
100^-  of  cone.  NH4OH  and 
600  c.c.  of  water,  and  after  solu- 
tion is  complete  dilute  to  one 
liter. 

Ammonium  chlorid,  (100). 

Ammonium  hydroxid,  (250)  of 
cone.  NH4OH. 

Ammonium  molybdate.  Dis- 
solve $og-  of  molybdic  acid  in 
a  mixture  of  100^-  of  cone. 
NH4OH  and  I$QC.C.  of  water. 
Dilute  250^-  of  cone,  nitric 
acid  with  $QQC.C.  of  water  and 
pour  into  first  solution  slowly 
and  with  constant  stirring. 
Let  stand  in  a  warm  place  for 
48  hours  and  decant  the  clear 
supernatant  solution  for  use. 


Ammonium  nitrate,  (25). 

Ammonium  oxalate,  (50). 

Ammonium  polysulfid.  Dis- 
solve some  sulfur  in  ammo- 
nium sulfid  solution. 

Ammonium  sulfid.  Pass  H2S 
into  one  liter  of  cone.  NH4OH 
to  saturation.  Then  add 
750  c.c.  cone.  NH4OH  and  one 
liter  of  water. 

Ammonium  sulfocyanid  (also 
called  thiocyanate),  (10). 

Antimony  chlorid.  Dissolve 
25^-  in  a  mixture  of  250^- 
of  cone.  HC1  and  750  c.c.  of 
water. 

Arsenic  chlorid.  Dissolve  50^- 
sodium  arsenite,  Na3AsO3, 
in  i  ,000^-  c.  of  water  and  add  in 
small  portions  cone.  HC1  until 
further  addition  occasions  no 
effervescence. 

Barium  carbonate.  In  suspen- 
sion in  water. 


Tables 


xxix 


Barium  chloric! ,  (60). 

Barium  hydroxid.  Dissolve  50^- 
in  one  liter  of  hot  water,  let 
stand  over  night,  and  filter  or 
decant.  Keep  in  tightly 
stoppered  bottle. 

Bismuth  nitrate,  (25).  The  solu- 
tion must  contain  a  little  free 
nitric  acid. 

Boric  acid,  (40).  Saturated  solu- 
tion. 

Bromin  solution.  Dissolve  2^- 
of  KBr  in  250 c.c.  of  water, 
add  6<£"-  (2  c.c.)  of  bromin,  and 
shake  until  bromin  is  dis- 
solved, 

Bromin  water.  Put  4o<?"-(i3  c.c.) 
in  a  liter  of  water.  Keep  bot- 
tle tightly  stoppered  and  in 
the  dark. 

Cadmium  chlorid,  (25). 

Calcium  chlorid,  (25). 

Calcium  hydroxid,  (lime  water). 
Put  some  freshly  slaked  lime 
in  a  bottle,  fill  bottle  with 
water,  shake,  and  when  solu- 
tion is  clear,  decant  and  reject 
'it,  as  it  may  contain  some 
impurities  from  the  lime. 
Fill  the  bottle  with  water 
again  and  shake  well. 

Calcium  sulfate.  .  Prepare  satu- 
rated solution  in  same  manner 
as  lime  water  above. 

Chromium  chlorid,  (25).  To 
ijoooc-c.  of  potassium  dichro- 
mate  solution  add  $oc.c.  of 
cone.  HC1  and  25  c.c.  of  alco- 
hol. Boil  for  half  an  hour 
gently  and,  if,  after  standing 
over  night,  the  solution  is  not 


clear  green  add  more  alcohol 
and  boil  again. 

Chromium  sulfate,  (30). 

Chlorin  water.  Pass  chlorin 
gas  into  water  until  it  smells 
strongly  of  the  gas.  Better 
make  small  quantities  when 
needed  by  adding  a  little 
cone.  HC1  to  a  few  crystals  of 
KC1O3  in  a  test  tube  and  as 
soon  as  the  gas  escapes  from 
mouth  of  tube,  adding  water 
to  stop  reaction. 

Cobalt  chlorid,  (50). 

Cobalt  nitrate,  (35). 

Cochineal.  Grind  a  little  with 
water  and  dilute  to  desired 
tint. 

Copper  nitrate,  (40). 

Copper  sulfate,  (35). 

Disodium  hydrogen  phosphate, 
(120). 

Ferric  chlorid,  (100). 

Ferrous  sulfate.  Dissolve  i5o<?"- 
of  clear  crystals  in  one  liter 
of  water,  and  add  5  c.c.  of  cone. 
H2SO4  and  a  few  pieces  of 
iron  (tacks  or  small  nails). 

Hydrochloric  acid,  (250)  of  cone, 
acid. 

Indigo.  Slowly  add  lotf-  of 
powdered  indigo  to  25  c.c.  of 
fuming  sulfuric  acid.  Let 
stand  for  a  day  and  then  add 
slowly  with  constant  stirring 
to  one  liter  of  water. 

Lead  acetate,  (90). 

Lead  nitrate,  (40). 

Litmus.  Grind  a  little  with 
water  to  a  paste  and  dilute  to 
desired  tint. 


XXX 


Elementary  Chemistry 


Magnesium  chlorid,  (25). 

Magnesium  sulfate,  (100). 

Manganous  chlorid,  (75). 

Manganous  sulfate,  (35). 

Mercuric  chlorid,  (30). 

Nessler's  Reagent.  Dissolve 
35^"-  of  potassium  iodid  in 
100  c.c.  of  water  ;  also  dissolve 
16^"-  of  mercuric  chlorid  in 
300^-^  of  water.  Add  the 
latter  solution  to  the  former 
slowly  with  constant  stirring 
until  the  precipitate  ceases  to 
be  redissolved.  Then  add  a 
solution  of  65<?"-  of  potassium 
hydroxid  in  60  c.c.  of  water 
and  filter.  Put  the  solution 
into  a  number  of  small  bottles 
and  cover  the  corks  with  par- 
affin. Keep  in  a  cool,  dark 
place,  and  when  the  solution 
is  needed,  do  not  open  more 
than  one  bottle  at  a  time. 

Nickel  chlorid,  (25). 

Nickel  nitrate,  (35). 

Nitric  acid,  (250)  of  cone.  acid. 

Phenolphthalein.  Dissolve  one 
gram  in  IOQC.C.  of  alcohol  and 
dilute  with  water  until  a  pre- 
cipitate begins  to  form  ;  then 
add  enough  alcohol  to  clarify 
solution. 

Platinum  chlorid.  Use  com- 
mercial solution,  or,  dissolve 
scrap  platinum  in  aqua  regia, 
evaporate  nearly  to  dryness, 
and  dissolve  residue  in  enough 
water  to  make  about  10  per 
cent  solution. 


Potassium  bromid,  (30). 

Potassium  chromate,  (100). 

Potassium  chlorid,  (50). 

Potassium  dichromate,  (50). 

Potassium  ferricyanid,  (30). 

Potassium  ferrocyanid,  (50). 

Potassium  hydroxid,  (150). 

Potassium  iodid,  (25). 

Potassium  nitrate,  (100). 

Potassium  sulfate,  (100). 

Potassium  sulfocyanate,  (50). 

Silver  nitrate,  (40).  Keep  in 
amber  glass  bottle. 

Sodium  acetate,  (130). 

Sodium  ammonium  phosphate, 
(7o). 

Sodium  chlorid,  (100). 

Sodium  hydroxid,  (175). 

Sodium  sulfite,  (200). 

Stannous  chlorid.  Dissolve 
So.?"-  in  IOQC.C.  of  hot  cone. 
HC1  and  keep  a  few  pieces  of 
tin  in  the  solution.  Make 
only  when  needed,  as  it  does 
not  keep  well. 

Starch  paste.  Grind  about 
lotf-  to  a  paste  with  a  little 
cold  water,  then  boil  with 
250  c.c.  of  water  until  clear. 

Strontium  chlorid,  (30). 

Strontium  nitrate,  (30). 

Sulfuric  acid,  (250)  of  cone.  acid. 
Pour  acid  in  small  portions, 
with  stirring,  into  the  full 
amount  of  water  required  for 
dilution. 

Tartar  emetic,  (100). 

Zinc  chlorid,  (50). 

Zinc  sulfate,  (140). 


APPENDIX  E 

SIGNIFICANT    FIGURES    AND    FORMS    OF 
RECORD   IN   QUANTITATIVE   WORK 

All  the  figures  of  a  number  are  called  significant 
excepting  the  ciphers  at  the  right  of  a  whole  number 
and  the  ciphers  at  the  left  of  a  decimal  fraction  ;  thus, 
the  significant  figures  of  30,600  as  well  as  of  0.000306 
are  306. 

In  all  measurements  one  significant  figure  more  than 
is  known  to  be  correct  is  kept  in  the  number  express- 
ing the  result  of  the  measurement ;  this  figure  is  said 
to  be  the  least  accurate  figure  or  the  doubtful  figure  of 
the  number.  Thus,  suppose  the  volumes  of  water  dis- 
placed from  an  aspirating  bottle  in  three  determinations 
of  the  weight  of  a  liter  of  oxygen  (Experiment  16)  were 
found  to  be  in  each  case,  1685  c-c-,  1680  c-c-,  and  1689  c-c-  , 
the  sum  of  these  three  numbers  is  5054,  and  their  mean 
is  1684.666  -f  c.c.9  or  1684.66!  c-c;  or  1684.67^-.  No  one 
of  these  is  proper,  for  each  assumes  a  greater  accuracy 
than  we  have  any  warrant  for  ;  moreover,  the  second  is 
irrational  in  its  combining  a  common  with  a  decimal 
fraction.  The  three  determinations  differ  in  units' 
place  ;  hence,  we  are  not  sure  of  units'  place.  We  must 
accordingly  drop  the  entire  decimal  part  of  the  average 
number ;  but  as  the  decimal  is  greater  than  0.5,  it  is 
customary  to  change  the  figure  4  in  the  average  to  5,  so 
that  the  average  is  1685.  If  the  decimal  had  been  less 
than  5,  it  would  have  been  dropped,  and  the  average 
would  have  remained  1684. 

[  xxxi  ] 


xxxii  Elementary  Chemistry 

Again,  suppose  that  in  three  weighings  of  a  dish  the 
following  results  were  obtained:  24.^^^-^  24. 35^-,  and 
24.32^-.  The  sum  of  these  numbers  is  73.00,  and  their 
average  arithmetically  may  be  24.3333  +  or  24-33y,  but 
if  the  above  rules  be  observed,  the  average  must  be 
24.33.  It  is  to  be  noted  that  the  sum  is  given  as  73.00 
and  not  as  73.  By  writing  the  two  ciphers  in  the  deci- 
mal we  indicate  that  we  know  that  the  tenths  and  hun- 
dredths  are  zero,  while  the  73  without  the  ciphers  leaves 
us  in  doubt. 

Let  another  illustration  emphasize  this  last  point. 
Suppose  the  weight  of  a  vessel  be  found  on  a  balance 
sensitive  to  a  hundredth  of  a  gram,  but  that  neither  the 
tenths  nor  the  hundredths  gram-weights  are  needed 
to  secure  equilibrium,  ilf  only  the  ten-  and  two-gram 
weights  are  on  the  pan  of  the  balance,  its  weight  is 
written  i2.oo<?"-  and  not  just  12^-.  The  ciphers  indicate 
the  degree  of  accuracy  attained.  They  mean  that  the 
tenths  and  hundredths  were  tried  in  determining  the 
weight,  but  were  not  needed.  By  expressing  a  weight 
as  12.00^-  you  indicate  that  a  balance  sensitive  to  hun- 
dredths of  grams  was  used,  while  12.0^-  would  mean 
that  a  balance  sensitive  only  to  tenths  of  grams  was 
employed. 

In  the  directions  for  the  quantitative  experiments 
the  degree  of  accuracy  is  denoted  by  the  number  of 
decimal  places  kept  in  specifying  a  quantity  to  be  taken. 
Thus,  in  Experiment  46,  exactly  2.00^-  are  specified, 
which  means  that  on  a  balance  sensitive  to  hundredths 
of  grams,  two  grams,  and  not  more  or  less  by  a  hun- 
dredth of  a  gram,  are  to  be  taken.  In  Experiment  16 
the  directions  are  to  take  about  5  &•  of  manganese  dioxid. 
This  quantity  may  be  weighed  roughly,  that  is,  to  about 
a  gram,  it  making  no  difference  if  4^-  or  6^-  should  hap- 
pen to  be  taken.  If  the  amount  had  been  written  5.0  &-, 


Significant  Figures  and  Forms  of  Record   xxxiii 

it  would  have  been  necessary  to  use  a  more  sensitive 
balance  and  weigh  to  tenths  of  grams. 

Suppose  that  it  were  found  that  2.68<^-  of  oxygen 
occupied  a  volume  of  1,871  c-c-,  i.  e.,  1.871  L.  Then  the 
quotient  of  2.68  divided  by  1.871  gives  the  weight  of  one 
liter.  The  question  arises  :  How  many  figures  of  the 
quotient  are  to  be  retained  ?  It  is  apparent  that  if  only 
weighings  to  hundredths  of  grams  were  made,  then 
only  hundredths  should  be  kept.  Accordingly  the 
quotient  is  1.43. 

Arithmetical  operations  on  data  obtained  in  quanti- 
tative experiments  may  be  much  abbreviated,  with  no 
loss  in  accuracy,  by  dropping  after  an  operation  of  mul- 
tiplication or  division  all  except  the  significant  figures 
in  a  number. 

To  illustrate,  let  us  solve  the  following  problem  : 
Find  the  reduced  volume  of  283  c-c-  of  a  gas  measured 
at  662  >«>»•  and  22°. 

It  is  to  be  noted  that  no  one  of  the  three  numbers 
given  has  more  than  three  figures  ;  hence,  there  are 
only  three  significant  figures.  Substituting  in  the  for- 
mula (§  27),  we  have 


Below  are  given  two  calculations  of  the  value  of  V, 
the  one  to  the  right  retaining  all  figures  after  each  mul- 
tiplication, the  one  to  the  left  retaining  in  each  product 
only  three  (significant)  figures. 

283  283 

273  273 


849 
1981 
566 

77259  77259 

3b 


xxxiv  Elementary  Chemistry 


773  77259 

662  662 


4638  463554 

4638  463554 

5^726  5H45458 

295  295 

760  760 


17700  17700 

2065  2065 

224200  224200 

224)  512(228.5  224200)  51145458  (228.1 

448  " 


_ 

640  6305 

448  4484 


1920  18214 

I792  17936 

1280  2785 

As  is  seen,  the  reduced  volumes  differ  only  in  the 
first  decimal  place.  But  as  the  units  are  doubtful,  the 
tenths  are  not  significant.  As  the  tenths  in  228.5  ig  °-5> 
the  number  according  to  custom  is  increased  to  229.  It 
is  thus  manifest  that  the  abbreviated  operations  give  as 
good  results  as  the  detailed  one. 


FORMS   OF   RECORD   OF   DATA 

It  always  saves  time  and  energy  to  enter  data  as  soon 
as  obtained  in  some  approved  tabular  form.  Always 
use  a  note  book,  never  a  scrap  of  paper.  Preserve  all 
the  arithmetical  work  so  that,  if  necessary,  it  may  be 
checked  up  with  a  second  determination.  Some  forms 
of  tabular  entries  are  given  at  the  end  of  the  directions 


Forms  of  Record  of  Data  xxxv 

for  the  performance  of  various  experiments.  A  very 
common  operation  in  quantitative  work  is  the  fol- 
lowing : 

A  dish  or  other  vessel  is  weighed,  some  substance 
placed  in  it,  and  a  second  weighing  made.  The  differ- 
ence in  the  weights  gives  the  weight  of  the  substance. 
A  good  form  of  record  for  this  operation  is  this  : 

Wt.  of  dish,  crucible,  or  test  tube  +  substance =  47. 63^"- 

Wt.      "         _.. _ =  23.42^"- 

Wt.  of  substance =  24. 21^"- 

Suppose  a  substance  is  being  heated  to  constant 
weight  in  an  evaporating  dish.  A  convenient  form  of 
record  is  the  following : 

Wt.  of  dish  +  substance  after  heating  for  20  min =  47.84^- 

Wt.      "        +  "         "    10     "     more  =  47.67^- 

Wt.  +  "    10     "        "     =  47.63<r- 

Wt.      "         +          "  "  "         "    10     "         "      =  47.63^- 

Wt.      " =  23. 42 <r- 

Wt.  of  substance =  24. 21^"- 

Other  similar  forms  may  be  readily  devised  by  the 
student.  It  is  a  good  plan  to  decide  upon  what  form 
of  record  is  to  be  used  before  commencing  a  quantita- 
tive experiment.  The  very  preparation  of  a  form  often 
helps  wonderfully  in  keeping  track  of  the  steps  in  an 
experiment. 


APPENDIX  F 


LABORATORY   EQUIPMENT 

The  subjoined  lists  contain  the  apparatus  and  the  chemicals 
required  for  the  experiments  in  this  book.  Prices  and  quantities 
have  not  been  given,  but  the  author  will  be  pleased  to  give  infor- 
mation to  teachers  using  the  book  as  to  the  quantities  of  apparatus 
and  chemicals  used  by  his  own  classes.  Prices  may  be  obtained 
from  any  of  the  dealers  in  chemical  supplies. 


LIST  A 

i 

INDIVIDUAL  APPARATUS 

This  list  comprises  the  pieces  of  apparatus  constantly  used  by 
a  single  student,  who  should  be  provided  with  each  piece. 

Iron  tongs. 
Platinum  wire. 
Blowpipe. 
Iron  forceps. 
'Triangular  file,  6". 
'Round  file,  8". 
Wire  gauze  or  asbestos  board. 
'Wing-top  burner. 
Mortar  and  pestle,  4". 
Iron  spoon. 
2Derlagrating  spoon, 
i  2Glass  rod,  5". 
i   Two-hole  rubber  stopper  to 

fit  large  test  tubes. 
3   ft.  rubber  tubing,  3/16". 
3   ft.  glass  tubing,  medium  wall, 


Test  tubes, 

Test  tubes,  6x^". 

Test  tubes,  gx  i". 

Beaker,  100  c.  c. 

Beaker,  250  c.  c. 

Flask,  100  c.  c. 

Flask,  250  c.  c. 

Retort,  250  c.  c. 

Glass  plates,  4x4". 

Thistle  tube. 

Funnel,  2^". 
'Porcelain  crucible,  i  oz. 
'Pipestem  triangle. 

Evaporating  dish,  3". 
2Test-tube  holder. 
2Test-tube  brush. 

Test-tube  rack. 


to  fit  rubber  stopper. 


1  These  pieces  of  apparatus  may  be  used  by  several  students  in  common. 

2  These  pieces  of  apparatus  may  readily  be  made  by  the  student  himself. 

[  xxxvi ] 


Laboratory  Equipment 


xxxvii 


LIST  B 

TABLE  APPARATUS 

This  list  includes  the  apparatus  which  should  be  kept  at  the 
laboratory  desk  used  by  the  student  or  on  a  side  table.  It  is  a 
part  of  the  equipment  to  be  used  by  different  classes. 

'Mohr  pinch-cocks. 

'Iron  and  copper  wire. 

'Sand. 

'Graduated  cylinders,  looc.  c. 
and  500  c.  c. 

'Bar  magnets. 

'Splinters  of  wood. 

'Wax  tapers. 

'Meter  sticks. 

'Trip  scales  and  weights. 

'Chaslyn  balances. 

i  It  is  not  feasible  to  give  quantities  for  these  articles ;  as  many  as 
possible  should  be  provided,  although  it  is  possible  to  get  along  with  few. 


i    Retort  stand  with  two  rings 

and  a  clamp. 
6   Wide-mouthed    bottles    or 

receivers. 

i    Pneumatic  trough, 
i    Bunsen  burner. 
3   ft.  rubber  hose  for  attaching 

Bunsen  burner. 
'"Acid  bottles." 
'Assorted  corks. 
'Hofmann  screw-cocks. 


LIST  C 
DEMONSTRATION  APPARATUS 

This  list  comprises  the  apparatus  which  the  teacher  should 
have  for  demonstrating  experiments.  It  should  be  of  the  best 
quality  and  not  mere  makeshift. 


i    Eudiometer  and  trough, 
i    Electrolysis   of  water  appa- 
ratus. 
i    Safety  tube. 

1  Kipp's  gas   generator  (it  is 

well  to  have  two  or  three 
all  charged  and  ready  to 
deliver  at  any  time  such 
gases  as  hydrogen,  carbon 
dioxid,  etc.). 

2  U-tubes,  6"  and  8". 
i    Liebig's  condenser. 


Thermometer. 
Bulb  tube. 
Induction  coil. 
Battery  to  run  coil. 
Large  lamp  chimney. 
'Rubber  stoppers   of  various 

sizes. 

'Ignition  tubes. 
'Supply    of    glass    tubing  of 

various  sizes. 

'Supply  of  rubber  tubing  of 
various  sizes. 


i  Refer  to  note  in  List  B. 


XXXV111 


Elementary  Chemistry 


LIST  D 

CHEMICALS 

The  chemicals  should  as  far  as  possible  be  of  "  c.  p."  grade. 


Acid,  acetic. 

citric. 

hydrochloric. 

nitric. 

oxalic. 

pyrogallic. 

sulfuric. 

tartaric. 
Alcohol,  ethyl. 

methyl. 
Alum,  chrome. 

potash. 
Aluminum,  metal. 

sulfate. 
Ammonium,  chlorid. 

hydroxid. 

nitrate. 

oxalate. 

sulfid. 

Antimony,  metal. 
Arsenic,  metal. 
Arsenious  oxid. 
Asbestos. 
Barium,  chlorid. 

nitrate. 
Bismuth,  metal. 

nitrate. 

Bleaching  powder. 
Borax. 

Cadmium  chlorid. 
Calcium,  carbid. 

carbonate  (marble). 

chlorid. 

fluorid. 

oxid  (lime). 

sulfate  (gypsum). 


Carbon  bisulfid. 
Charcoal,  animal. 

wood. 
Coal,  hard. 

soft. 
Cobalt,  chlorid. 

nitrate. 
Cochineal. 
Copper,  metal. 

nitrate. 

sulfate. 
Ether. 
Glycerin. 
Indigo, 
lodin. 
Iron,  metal  (filings  and  wire). 

chlorid. 

sulfate. 

sulfid. 
Lead,  metal. 

nitrate. 

monoxid  (litharge). 

red. 
Litmus, 

paper. 

Magnesium,    metal   (powdered 
and  ribbon). 

sulfate. 
Manganese,  dioxid. 

sulfate. 
Mercury. 
Mercuric  chlorid. 

nitrate. 

oxid. 

Mercurous  nitrate. 
Nickel  chlorid. 


Laboratory  Equipment  xxxix 

Phenolphthalein.  Sodium,  metal. 
Picture  cord  (iron).  bicarbonate. 

Potassium,  metal.  carbonate. 

bromid.  chlorid. 

carbonate.  hydroxid. 

chlorate.  nitrate. 

chromate.  phosphate. 

dichromate.  silicate. 

ferricyanid.  sulfate. 

ferrocyanid.  sulfite. 

hydroxid.  Stannous  chlorid. 

iodid.  Starch. 

permanganate.  Strontium  nitrate. 

sulfate.  Sulfur,  flowers  and  roll. 

sulfocyanid.  Tin,  granulated. 

Rosin.  Vaseline. 

Silver  nitrate.  Zinc,  granulated  and  sheet. 
Soda-lime.  sulfate. 


W^TT^ 


-5, '43  (6061S) 


V/D       \   /  r\  /    * 
ID       IDOO»4 


50 


